My theory

I am absolutely sure Zara is Indira and the whole death thing can be explained this is how Zara was a lookalike a diligent police officer who found out her husband is a terrorist, she confronted him a fight ensued zara got seriously hurt and ended up comatose, I'm guessing the husband is a doctor judging from the rishi incident.He took her to delhi to avoid suspicion lying to family members about her whereabouts Zara's condition worsened he was stuck in a jam her death will cause suspicion and unnecessary attention meanwhile at SN Indira was becoming more resposive (remember how her hand moved when rishi placed Indu on her that was major) rishi decided to take her to hospital hopeful Zara's husband saw them became informed about her condition, in a panic he exchanged Zara with Indira(probably she was awake by then and suffering from memory loss unbeknownst to rishi) he took her tomumbai where by showing her pictures and family members convinced her she is Zara. The thing he wasn't counting on was Indira sharma the personality traits we've all seen how similar they are but while Zara was a decent cop, Indira as Zara turned out to be a great cop he decided to move to delhi to escape her eyes also because Indira could not bear to bring herself closer to him (the child remark hinted by Zara's SIL indicated this) so he moved also to make her comfortable.This will also explain rishi's attitude he must have been devasted to learn his wife who was showing signs of recovering died he was so close but failed to cure her grief made him blind so he also couldn't see the difference plus I'm thinking this will please inshi and zashi fans cause if she is Indira the Zara influence is going nowhere.