What is the latest point of time when Iran/Persia could remain or return to being a predominantly Zoroastrian country? Could the Safavid dynasty, if they had wanted, have converted the country to Zoroastrianism instead of Shia-Islam?
Potentially till today, unless Turks, Mesopotamian Nestorians or Orthodox Romans takeover, if you choose to kill or curb Islam. And considering the Safavids were Muslims, and Persia was already Zoroastrian, why would they do that?
Sacking of Baghdad taken as a sign that Islam is no longer favored, a native Persian dynasty rises with strong commercial ties to the Parsi of India eventually marrying one and Zoroastrianism filters into the populace as a plurality religion with time?
Khorzan was still Parsi about this time, there are plenty of families who might step up under the right circumstances. Also if Timur decides that Islam is nice but something more unique might make him fit his Persian and Turkish subjects more maybe under the wrong set of circumstances he converts, especially as a concept of "holy fire" could be used for all sorts of atrocities that Zoroastrianism never intended.
What would possess Timur out of all people to convert to Zoroastrianism? The moment that he converts is the moment he can kiss his throne goodbye and become a historical footnote. Islam by the 9th century wasn't perceived as a foreign faith but as part of Persian identity. The man credited his military and political victories to Allah, not to any other deity. His advisors were all Islamic (Sunni) scholars. Converting to a dying religion would stand against everything that Timur was as a person.
Well, the simplest solution is to have the country never be conquered by the Arabs in the first place. This was not necessarily an inevitability.
http://en.wikipedia.org/wiki/Mardavij
This man was the last serious Zoroastrian ruler in Persia, anything else afterwards might as well be ASB
http://en.wikipedia.org/wiki/Mardavij
This man was the last serious Zoroastrian ruler in Persia, anything else afterwards might as well be ASB