Looks really cool.
But I think the gore/blood is too much.
Its too much of a cartoon with Ketchup-bottles.
The gore should be more of an reward, for example when managing to blow of
a limp or head. Else it should just have normal impact animations.

Its also cool if the player could have some tactics:
-Head: harder to shoot but higher damage
-torso easy to hit, low damage
-arms: harder to hit, but zombie looses weapon
-legs: medium to hit, but zombiw walks much slower, or
falls over for some time.

The time-effect is cool, but for this
to be useful you also need some fast-paced action
(like approaching rockets, jump+shooting),
the zombies are quite slow, so the timeeffect is not very useful.

(also check that all soundeffects are propertly licensed)