Zarathustra was one of the Avatars according to Meher Baba. "When man becomes God and retains creation-consciousness, he is called a Man-God; but when God becomes man, He is called the God-Man, or the Avatar. - Meher Baba.

The Gathas of Zarathushtra
Hymns in Praise of Wisdom.
173 pp
Translation and commentary by Piloo Nanavutty.
Zoroastrianism is the religion into which Meher Baba was born. It grew out of the life of Zararthushtra, the Prophet of Ancient Iran. This beautifully produced book is a good introduction to Zoroastrianism, including as it does the seventeen "Gathas" or hymns composed by Zararthushtra and which contain the core of his religion. Nanavutty has translated the Gathas into idiomatic English and provided helpful commentaries. Rich color illustrations from various sources enhance the text.
Published 1999.