I thought dat Zubbu may have killed Kabir cuz he may have thought dat Udita may back off in d last moment after Kabir will explain her so he may have killed him to blackmail her using d crime she never committed. So acc. to him, Udita only killed him n he rememebers police seeing Kabir n Udita's dead bodies. So, may be it will be found dat Anushka killed Kabir cuz he rejected her for Udita. Then she may have willingly or unwillingly married Zubbu only to be killed by him later.