LOL! Yeah that’s another thing, it doesn’t matter what they use, a knife, a stick, a spike, these zombie skulls always smash open like they are made of eggshells lol. Oh yeah, and stomping, that also smashes their heads open like it’s made of watermelon.
Perhaps it is easy to smash their heads due to decay from within.
Any penetration of the skull, however slight, ensures TWD zombie death. I noticed early on that its a rule they are going with. Don’t worry about the brain stem, a 2” incursion into the frontal lobe instantly kills a zombie, even though its quite survival for a living person.