The idea that Zoroastrianism and its beliefs and practices have been influenced by other religions, including the Babylonian and Hellenistic religions, Judaism, and Islam, has been put forward by many scholars, like James Darmesteter,

Influence of Elamite religion

Mary Boyce has suggested that the prominence of Humban in the Neo-Elamite period influenced the position of Ahura Mazda in later religious traditions of the Persians.Henkelman, Wouter F. M. (2008). The other gods who are: studies in Elamite-Iranian acculturation based on the Persepolis fortification texts. Leiden: Nederlands Instituut voor het Nabije Oosten. . page. 364. In the Persepolis Administrative Archives, Humban appears more commonly than any other Elamite or Persian deity, with a total of 26 mentions, compared to only 10 for Auramazdā, an early form of Ahura Mazda.Henkelman, Wouter F. M. (2008). The other gods who are: studies in Elamite-Iranian acculturation based on the Persepolis fortification texts. Leiden: Nederlands Instituut voor het Nabije Oosten. . page. 353. Henkelman, Wouter F.M. (2017). "Humban & Auramazdā: Royal Gods in a Persian Landscape". Persian Religion in the Achaemenid Period/La Religion Perse à l'époque Achéménide. Harrassowitz Verlag. pp. 273–346. page. 306, 313, 319 Overall he received the most offerings of all deities attested in textual sources.Henkelman, Wouter F.M. (2017). "Humban & Auramazdā: Royal Gods in a Persian Landscape". Persian Religion in the Achaemenid Period/La Religion Perse à l'époque Achéménide. Harrassowitz Verlag. pp. 273–346. . , page. 315 The amount of grain offered to him by the Achaemenid administration was more than thrice as big as that offered to Auramazdā.Henkelman, Wouter F. M. (2008). The other gods who are: studies in Elamite-Iranian acculturation based on the Persepolis fortification texts. Leiden: Nederlands Instituut voor het Nabije Oosten. . page. 353 Offerings to him are designated as bakadaušiyam in multiple cases.Henkelman, Wouter F.M. (2017). "Humban & Auramazdā: Royal Gods in a Persian Landscape". Persian Religion in the Achaemenid Period/La Religion Perse à l'époque Achéménide. Harrassowitz Verlag. pp. 273–346. . page. 310.

Wouter F. M. Henkelman suggests that, in this period, he should be regarded as a Persian god, rather than a strictly Elamite one, and that the references to the bakadaušiyam of Humban are likely to reflect his popularity and status as a royal god.Henkelman, Wouter F. M. (2008). The other gods who are: studies in Elamite-Iranian acculturation based on the Persepolis fortification texts. Leiden: Nederlands Instituut voor het Nabije Oosten. . page. 310, 315–16, 374. This Elamite term is a loan from Old Persian, and can be translated as "(feast) of the offering to (a) god", and likely designated a public feast. Similar celebrations are attested only for a small number of other deities.

Influence of Ancient Iranian religion

Ahura Mazda is a very ancient deity that precedes Zoroastrianism. As is common in new religions, when founding his faith, Zoroaster utilized this established name to designate the supreme God. The abstract name Mazda predates Zoroastrianism, and even the fundamental role assigned to this deity in Mazdeism is not a Zoroastrian innovation. Henrik Samuel Nyberg suggests that none of the essential characteristics of Zoroastrianism are present in the fundamental structures of the Achaemenid religion. The Achaemenid religion lacked any of the technical terms from the circle of Zoroaster, any distinct ideas characteristic of the Gathas, and any specific beliefs or practices unique to the Zoroastrian faith. He therefore concludes that the foundational background of the Achaemenid religion is the Ancient Iranian religion.

Though Achaemenid texts use of the terms Mazdayasna (Mazda-worshipper) and Ahura Mazda, they do not mention Zoroaster, nor is there any other indication that these inscriptions denote a Zoroastrian character. Jacques Duchesne-Guillemin writes, "It seems simpler to think that the Achaemenids had never heard of Zoroaster or his religious reforms."

Influence of Babylonian and Greek religions

Emergence of Zurvanism

Some scholars believe that the emergence of Zurvanism was due to the contact of Zoroastrianism with the Babylonian and Greek religions, but also some believe that Zurvan was a god of the Medes religion and his worship continued in Zoroastrianism.

Influence of Judaism

Zoroaster and Jews

Various Jewish and Christian traditions exist regarding a connection between Zoroaster and the Jews; these traditions are divided into two categoriesthose that view Zoroaster negatively and those that view him positively.

Several Jewish and Christian traditions recorded in the Book of the Bee state that Zoroaster was Baruch, but he changed his name to Zoroaster. Theodore bar Konai identified him as an Israelite from the city of Samaria who had been taken captive during the Assyrian exile. Muslim scholars from among the People of the Book reported that he was a disciple of the Prophet Jeremiah, Elijah, or Ezra.

Thomas Hyde viewed Zoroaster positively, regarding him as a religious reformer who had studied under Jewish prophets such as Ezra the Scribe. Humphrey Prideaux noted that Zoroaster possessed extensive knowledge of Judaism and its sacred scriptures, leading him to surmise that Zoroaster was either Jewish by birth or a follower of the Jewish faith; however, Prideaux held a negative view of Zoroaster, regarding him as one of history's greatest impostors and false prophets.Humphrey Prideaux, Iife of Mohammet, pp310-311

Saoshyant

Dr. Ardeshir Khorshedian, a Mobad and the head of the Mobidan Association of Tehran, said the idea of the Zoroastrian Saoshyant as a Messiah figure likely came from Judaism, and became more prevalent following the Islamic conquest of Persia. Mobad Cyrus Niknam, a writer and researcher of ancient Iranian culture, says the idea of Saoshyant as a savior stems from the interpretations of Sasanian priests and is not supported by the teachings of Zoroaster himself. He says the name means benefactor of the holy. Dina G. McIntyre, an Indian Zoroastrian woman and a specialist in the study of the Gathas, sais the existence of a savior only appeared in later literature.

Farhang Mehr has said that the miracles attributed in the Pahlavi texts to Ashu Zarathustra or to the saviors after him, as well as his dialogues with Ahura Mazda and Amesha Spenta, do not exist in the Gathas but come from the Denkard, composed in the 10th century, centuries after the demise of the Sassanids. He suggests Zoroastrianism began to attribute miracles to Zoroaster that were on par with the miracles of the Abrahamic prophets in order to compete with the growing political supremacy of the Abrahamic faiths.

Zoroaster's life stories The Encyclopedia Iranica states that contact between Zoroastrians and their Jewish and Christian neighbors in the Achaemenian, Arsacid, and Sasanian states influenced the hagiography or sacred biography of Zoroaster. Drawing on events in the Gathas, the stories of Zoroaster's life developed themes similar to those of Moses and Jesus. Between the 7th and 13th centuries, this hagiography also developed several parallels with the life of Muhammed. This hagiography was thus included in the Zardošt-nāma and Dēnkard. As Zoroastrians were a minority among Muslims, Christians and Hindus, the parallels in these stories provided a source of common ground, especially as dimmi under Islam.

In the 19th century, visual representations of Zoroaster incorporated Mithraic, Platonic and Ptolemaic motifs, in part drawing from Raphael Santi's earlier, Italian Renaissance-era portrait of the prophet. These representations remain popular today.

Influence of Christianity

Parsis

In 1860s and 1870s, the linguist Martin Haug interpreted Zoroastrian scripture in Christian terms, and compared the yazatas to the angels of Christianity. In this scheme, the Amesha Spentas are the archangel retinue of Ahura Mazda, with the hamkars as the supporting host of lesser angels.

At the time Haug wrote his translations, the Parsi (i.e., Indian Zoroastrian) community was under intense pressure from English and American missionaries, who severely criticized the Zoroastrians for—as John Wilson portrayed it in 1843—"polytheism", which the missionaries argued was inferior to their own "monotheism". At the time, Zoroastrianism lacked theologians of its own, and so the Zoroastrians were poorly equipped to make their own case. In this situation, Haug's counter-interpretation came as a welcome relief, and was (by and large) gratefully accepted as legitimate.

Haug's interpretations were subsequently disseminated as Zoroastrian ones, which then eventually reached the west where they were seen to corroborate Haug. Like most of Haug's interpretations, this comparison is today so well entrenched that a gloss of 'yazata' as 'angel' is almost universally accepted; both in publications intended for a general audience as well as in (non-philological) academic literature.cf. .cf. .cf. .cf. .

Mary Boyce noted that the theories of the Western Academy had a profound impact on the Parsis in mumbay and mentioned M. Haug proposal regarding the Amesha Spentas, which states that they are merely attributes of Ahura Mazda. This was welcomed by the Parsi reformers, who were under attack from Christian missionaries who accused them of polytheism. These reformers strongly promoted Haug's ideas, and Western scholars considered their writings as evidence that Hogg's interpretation had a real echo in the Zoroastrian tradition itself. also noted that some reformers have adopted the belief that Ahura Mazda is the father of Ahriman and Amesha Spenta, and this is a belief invented by M. Haug

Jenny Rose notes that the Parsis were in harmony with Christianity, likening Zoroaster to Jesus and attributing miracles to him.

Pakistani Zoroastrian priest and religious scholar Maneckji Nusserwanji Dhalla says that when the Parsis tried to defend their religion from the criticisms of Christian missionaries, they resorted to metaphorical interpretation instead of defending beliefs, such as saying that Ahriman was a symbol of blasphemy and not a living entity, and that purification rituals were a metaphorical expression of the internal purification of man.

Also added that the Parsi conservatives accused the Parsi reformists of trying to transform Zoroastrianism into a Protestant sect under the influence of Christianity

Jean Kellens criticized the Zoroastrian tradition regarding the history of the Avesta, describing it as insufficiently documented. He pointed to historians' statements about the Magi, stating that they did not have a holy book, in addition to the fact that writing was not widespread among the Achaemenids, and the scarcity of written documents. He added that recent research has proven that the Avesta was not written during the Parthian Empire, and that the available manuscripts indicate that it was written during the Sassanian era. He pointed out that the Zoroastrian tradition regarding the composition of the Avesta dates back to its emergence as a competition with Buddhism, Manichaeism, and Christianity, which rely on their own holy books

Influence of Islam