Persians hold the Arabs back at the Zagros: what happens to the Umayyads?

[Nivek]

I don't think that Persians would accept the loss of Mesopotamia, so Arabs should focus more on the defence in Zagros, like in Taurus IOTL, especially if Romans and Persians will have alliance against the Caliphate

That was OTL, so OTL would happen and they got defeated as OTL.

 

[HyperMuscularDemon]

What about North Africa? If Persia holds back the early Islamic conquests, then Arabic commanders and Arabic armies could turn to North Africa and the Levant, as well as costal East Africa.