Zombie killing lesson of the day.(This is more sort of guesses)
There are generations of zombies. I believe it goes, leader zombie is strongest, people that are bitten by the leader zombie are wimpier, and the people they bite are yet even more wimpier.
The higher the generation you are, the wimpier. I believe third generations cant break r-walls, and I have yet to see regular walls be unclawable by one zombie. The big differance between generations is heal rate and health. Leader zombie has tons of regen and health. Generation 5 gets knocked out by 1-3 lasers. The last zombie game I had, I knocked out two zombies with one laser gun, and went in to beat them in the heads with a fire exstinguisher. It took a while(plus the one minute they have to wait before dieing) but they eventually did. They were probably bordering generation 4, and the one who got KO'ed in one shot was probably like generation 6 or something.
Also, I believe higher generations get harmed by cold. The first 1-3 generations dont, and the rest slowly do, getting worse as you go. That would explain the differant zombie experiences with space. But, when I get harmed, I might actually be auto healing, I sometimes missread the colar change. So there may actually be no damage, I might have to test this later
"Edit" Also, never leave a zombie to die, it WILL auto heal, in its last minute, pulling it out from the edge. Just keep hitting it in the head with a melee weapon and you will be fine, it will go down in a few minutes. Just beware other zombies, and if your in a hallway, drag the zombie corpse to a room.
"Edit2" I was thinking last night, what about giving the crowbar a higher potential melee damage against zombies than the fire exstinguisher? Give all current melee weapons 90% of their current damage potential against zombies, and give the crowbar 110% of the original damage the fire exstinguisher does. As it is known in zombie games, there is always a crowbar, and there is always zombie heads splitting open. Make it a tad more "zombie" in my opinion. Of course, then how would we implement it?