Indo-Iranian religion, founded by Zoroaster or Zarathustra, now generally placed between 1200 and 1000 bc. The dominant religion of Persia until the rise of Islam, Zoroastrianism is now largely confined to the Parsi community of Bombay. Its scriptures are known as the Avesta. It maintains a dualistic doctrine, contrasting the force of light and good in the world (Ahura-mazda) with that of darkness and evil (Ahriman, or Angra Mainyu). Offshoots of Zoroastrianism include Mithraism and Manichaeanism. Zoroastrianism entered the western tradition as an influence on Judaism, and hence on Middle Platonism. Zarathustra was the character invested with Nietzsche’s imaginings of a spiritual rebirth and a higher form of humanity in Also Sprach Zarathustra. (See also Übermensch).

http://www.bbc.co.uk/religion/religions/zoroastrian/ An outline of the main features of Zoroastrianism

http://www.bbc.co.uk/radio4/history/inourtime/inourtime_20041111.shtml An audio discussion on Zoroastrianism by three experts