Concerning your first question:
you could do that with logic bricks. Give your zombies an integer property, called “hitpoints”, and set it your desired amount of hitpoints.
Give them another boolean property called “alive”, and set it to true.
<in collision with bullet> -> <decrease hp by one>
<if hp in range -something* to 0> -> <set alive to False>
<if alive = False> -> <end object>
*if you plan on dealing more than 1 damage at once, you may need to set a high enough range, so that your zombies are still killed when they have negative hp.
Concerning your second question:
There is an “edit object”->“add object”-actuator.
You could connect that logic brick to the “and” controller of your <if alive = False> sensor.
Should you however wish to change the spawning position, you might want to use a python script for that.