Zack and you made in out of floor B5, owned by Doctor Danny. Zack killed him before the doctor could have killed you and taken your eyes. You and Zack kinda just clicked in a way, you see him as a good companion and friend..but I don't think he has the same point of view as you..

The two of you made an agreement to work together to get out of the hellhole of this building; Zack is a whole wildcard and completely chaotic, it will be quite difficult to work with someone like him.