Same way they can die from poison damage in games, game logic thats it. Now fire can work on a zombie, why you ask? well the weakpoint they have is the brain, and well when the zombie is buring it boils its brain killing it or at least thats a logical way to explain why fire works on zombies.
7 Days to Die is not realistic at all, work benches irl don't make stuff on their own, same for camp fires, etc, you can't bend metal in your bare hands, nor can you scrap metal things with your bare hands. Arguing realism with 7dtd is just a stupid arguement as its not realistic at all. I mean if you drank as much water as you have to in a average day in 7dtd irl you'd die as the water would thin your blood causing a bunch of issues including brain swelling, google it if you don't believe me, its an actual thing. As for food, only people who would eat that much would be a 600 lbs fat person. I could go on but you prob get the point. Zombies bleeding is by far the least of 7dtd ways it'd break reality. I mean zombies WOULD bleed as they DO usually have blood left in their body, but it wouldn't do any harm to them, as about only thing that can stop a lore accurate zombie is destroying the brain, even cutting its head off does not kill it, the head will still be moving the body will fall thou and its basically not a threat now, but its not actually dead.
