Yes, but they seem to fall apart a little TOO easily. I’m not saying I’ve seen a person get shot point blank with a shotgun before, and I know it’d do horrific damage, but the zombies gib and fall apart sorta’ve like their skin is made of paper. In fact in the L4D wiki they addressed this by making up theories as to why that is, such as the infection weakening their body. I’m not really saying this just from the shotgun but such as with the axe. I doubt hitting someone with an axe would slice through them as seemingly effortlessly as it does in L4D2. So, I’d like to see more realistic gibs and damage but not really to that extreme.
Typically in modern zombie stories, zombies are rotting corpses that happen to be able to move.
Not always (World War Z, Resident Evil movies as two examples where decomposition stops after a certain point) but most of the time.
That would explain some of their frailty, anyway.