Complex sentence: A prototype of Zoroastrian was the early religion of the Median Empire, and in varying forms Zoroastrianism was the generally-inclusive state religion of Greater Iran from 600 BCE to 650 CE, including the Achaemenid, Parthian and Sasanian Empires.
Split into simpler sentences: A prototype of Zoroastrian was the early religion of the Median Empire. In varying forms Zoroastrianism was the state religion of Greater Iran from 600 BCE to 650 CE, including the Achaemenid, Parthian and Sasanian Empires.