Suppose that the Acharmenid Empire of Persia survives (by defeating and annexing the greek city-states, defeating Alexander, what have you) for longer, at least until the early 1st century AD (of OTL).
My question is... how does this affect India?
I'll postulate a scenario: considering that Alexander either never existed or never achieved as much success ITTL, i'd presume that the Mauryan Empire never rises to prominence. The achaemenid persians end up trickling down into the subcontinent, and found some sort of zoroastrian indo-achaemenid kingdom, encompassing the Indus Valley and the Ganghes, that may outlive its persian patron. The kalingas of Orissa, which were actually pretty powerful IOTL, found their own empire, conquering Bengal and OTL Maharashtra.
If the persians decide to pursue a maritime focus in expansion, they could end up vassalizing the southern dravidian kingdoms and even conquering some ports. Buddhism never becomes as powerful as OTL and finds itself in a lot of competition with zoroastrians.