And based on the promo that comes a couple of days ago, Zara won't find out till the nikkah is complete... which is unfair. He should tell her before. Zeenat is extremely happy with both Kabeer and Zara and she initiated to start the wedding preparations that were left incomplete. so we will see a positive Zeenat for a little while till Ruksar and kabeer's Nikkah secret comes out. Afterwards I'm sure she will return to her old negative self and try to get her sister her right over Kabeer and most probably ask Zara to leave the house once again.
I really want Zara to find out before but knowing this the creators they wont do that.
Link to the BTS:
https://youtu.be/EMyl3s4SkBI