Zombies are spread around buildings, sleeping and some well hidden. They can abruptly wake up and attack you from anywhere, e.g. they could come through the roof, jump out of closets, etc.
There are zombie's which behave a little like spiders. They crouch, jump on you and make noises which are often used in games to represent spider enemies.
The Zombies are eating you if you die while they are near. The camera will stay on your body for a few seconds before you can revive. You are forced to watch them.
You can have broken bones as a consequence of fight or falling down. You will not see it on the character, but there is a bit of audio which gives a hint if you for example run with a broken leg.