As for now haider might have come to take revenge for his father alone and I guessed the revenge must be for his father and not zainab as they have mentioned baazigar story here in every article of his entry... but in the process of taking his revenge, he might find out about zoya and her past...and her relation with SM...then he might get friendly with her after knowing her past without revealing her past to her... and he is going to change her equation with SM from Bahu to bheti...