Those of you who believe that Zara is Indira, here is a possibility. I am trying to think like the writers of HD. So, any resemblance to logic (alive or dead) is purely incidental, coincidental, accidental, inadvertant, and unintentional.
Right now, Rishi thinks that Lahorewali is Indira because she has brain tumour and her thumb impression matches Indira's. Our HD writers, who are forever prone to twists, might want to consider a scenario in which Indira's and Zara's brains were swapped. Minor surgeries like this are commonplace, so they can be done in some deep, dark part of a jungle where no one would find out what's happening.
So, because of something that happened, the brain with the tumour (Indira's) was transplanted into Zara's skull (mostly by Malik to fulfil his dark intentions). Zara's healthy brain was given to Indira who Malik rescued off the burning pyre for the same dark intentions just mentioned. Don't ask what they were right now. We'll think of something when we get there.
So Zara, who has Indira's brain, also has the tumour and a faint memory of Rishi. And Indira, who actually has Zara's brain, neither has a memory of Rishi nor the tumour. That way, whoever wants Zara to be Indira is happy and the writers can congratulate themselves for entertaining us.