Zombie behavior works great with one zombie. Bit put a few together and something goes wrong. First of all the move synchronized which is funny and a but creepy but not what you want. Beside3s that the trigger don't work. They attack when you are not in reach or don't attack when you are.
You can kill them but they don't fall but freeze (by the way grenades lose their texture when you you throw them).
That you can kill them is fine but is not part of the y the behavior. may be we there should be an interrupt/trigger system like "if shot go to", "if loud sound move towards it" , "if hit and hit is turn undead spell move away" or "if stuck stop moving".
stinking zombie
I tried to make a stinking zombie, a smart object with a zombie and a particle emitter emitting a green cloud. But the emitter doesn't move with the zombie. (behavior is not save correctly in smart object)
spitting zombie
the same smart object with a spitting particle. Zombie hits left, right and then spit some disgusting particles. The make that possible it should be possible to have two objects in an behavior, hit left hit right and start particle wait stop particle hit left hit right etc.
maybe a message system between behaviors would be nice if shot fired send message, if message interrupt zombie and move to sound