I don't have a problem with the zombies vision/hearing too much, just go prone and be careful. The problem is that many buildings can't be entered without going into a crouch, when you have no weapons and you need to crouch for 2 steps to get over the doorstop, you're dead, since you agro every zombie within a 200m radius. After a respawn, the only place you're able to enter without agroing zombies are barns and other buildings with big doors.