You are using an out of date browser. It may not display this or other websites correctly. You should upgrade or use an alternative browser.
alternatehistory.com
If there was a scenario to the invasion of Persia that played out more like the Indian subcontinent where the muslim invaders were successful in their conquering of the lands but the majority of the population still retained their native religions?
So an Iran/Persia with a continued Zoroastrian majority.