I think Zoya signing the divorce papers itself is a huge sacrifice she's doing to save her father. One thing did u notice? When HH decided not to fight Zoya's case, Adi threatened him that he will confess that he killed PooSh so that Zoya will be saved. HH had no choice but to fight again for Zoya to save his son's life.
The opposite is happening now. Zoya is sacrificing her marriage with Aditya to save Waseem. Again a father is involved here too but in a different way so the consequence will also be different. This time Aditya will save their marriage.
I feel Aditya will not sign the divorce papers at all. Till now, Zoya fought the battle with NaRaj. After receiving the divorce papers, Aditya will come to picture and will defeat NaRaj.
The only thing I can hope is Waseem gets to know what his daughter did for him and accepts her again.