This is about the A.I of zombies who want to eat your brains. This is a list of their A.I. Note: all zombies infect you. To counter it bring antiviral pills.

Peasant Zombie Shuffling Zombie
Not too dangerous, slow, low health. Be careful not to get ganged by a horde of them.
Shuffling Zombie
Looks like the Peasant Zombie, only difference is that it moves somewhat faster (shuffles your way).
Zombie Soldier
Kill with ranged weapons. High attack, medium health and has a chance to drop its sword or a gun. On its own not too dangerous but if it has a friend who has tagged on run. Sometimes stops randomly and leans on its sword. However it can move surprisingly fast and so if one is not very far away run away/in circles.
Scientist Zombie
This zombie has 2 A.I types. First of all is the ranged A.I where it stays back and shoots balls of acid at you. Be careful for this one as if you don't have a ranged weapon it can be deadly. Second is the melee/chasing A.I where it runs after you and hits you with its needle contraption. Does high damage, has high health and a devastating ranged attack. Medium speed when chasing.
Burning Zombie
Is a harder peasant zombie. Easy to spot at night. More attack, speed and health than a peasant zombie. It also glows like a firefly. (you can see them from a mile away at night)
Elite Zombie Soldier
Is the same upgrade as fire peasant zombie but for military zombies. I only have seen them when I raided the middle. Has a red uniform.
Zomzilla aka Giant Zombie
5x more health than a normal zombie( I once had to shoot three stacks of ammo at 3 giant scientist zombies)
Do NOT melee them unless you are suicidal. Comes mostly in groups and will not move fast compared to its size. Very rare but easy enough to find if you hang around near Tesla Towers. Because of its size it is easy to spot and easy to hide from(hide inside). Not too dangerous if you count their rarity but avoid them if you can.
Testing Subject Zombie aka Crawler
Is fast, has medium damage and despite their gross appearance will eat your brains with ease. Do not underestimate these zombies- even more so in groups!