After Aton, then Came Zoroaster. Hebrews like to claim that their religion is the first to claim one god, but evidence exists that proves that the first Middle eastern example of monotheism came during one of the latter dynasties in Egypt.
No it isn't monotheistic. It is the first religion to have an idea of good and evil and the Hebrews acquired it from it. There are few left in the world too, I think fewer than half a million. The first monotheistic religion was sun worship in Egypt. Egypt made a brief attempt at monotheism, the other gods won the minds of the people though. Judaism borrowed monotheism from the Egyption attempt.
I have always understood that Zorastrianism is dualist rather than monotheist. However, if it was monotheist then it would be the second, as it is much older than Christianity.
The religion was founded by Zarathushtra (Zoroaster in Greek; Zarthosht in India and Persia). Conservative Zoroastrians assign a date of 6000 BCE to the founding of the religion; other followers estimate 600 BCE. Historians and religious scholars generally date his life sometime between 1500 and 1000 BCE on the basis of his style of writing.
He lived in Persia, modern day Iran. Legends say that his birth was predicted and that attempts were made by the forces of evil to kill him as a child. He preached a monotheism in a land which followed an aboriginal polytheistic religion. He was attacked for his teaching, but finally won the support of the king. Zoroastrianism became the state religion of various Persian empires, until the 7Th Century CE.
When Muslim Arabs invaded Persia in 650 CE, a small number of Zoroastrians fled to India where most are concentrated today. Those who remained behind have survived centuries of persecution, systematic slaughter, forced conversion, heavy taxes, etc. They now number only about 18,000 and reside chiefly in Yazd, Kernan and Tehran in what is now Iran. The Canadian 1991 census counted 3,190 Zoroastrians in that country. The actual number is believed to be much higher. According to the Fezana Journal survey, published quarterly by the Federation of Zoroastrian Associations of North America, there are about 11,000 Zoroastrians in the United States, 6,000 in Canada, 5,000 in England, 2,700 in Australia and 2,200 in the Persian Gulf nations.