Female Dormitory in the Apocalypse: My Key Can Open All Doors

[The end of the world + multiple female protagonists + decisive killing + not the Holy Mother + system] At the beginning, Zhang Ze went to the dormitory to return the items left behind by his ex-girlfriend. The end of the world is coming, and blood is pouring down. Zombies were sieging outside the dormitory building, and only the panicked female roommate was left inside the door. The two were trapped in the dormitory. After killing the mutant zombie housekeeper aunt in a desperate situation, I got a prop, a bronze key that can open all doors...