Isn't that part of the problem? Zombies die with no head, so not zombies...
Stopped playing RE4 fairly near the beginning, maybe half an hour in or something.
They are special zombies. Just because they aren't controlled by a virus, doesn't make them not zombies. And since you didn't play RE 4 that long, what gave you the right to judge it didn't have zombies? Some regular zombies appear later on in the game.
My true form. You like it?