This is a simple method to use (particularly in wider areas). Run around the Zombie (to get behind it) and slash it. You should not stand directly behind the Zombie, or it may turn around and (simultaneously) attack you.

Simply make sure that you are a safe distance away (and be careful). The Zombie which you are attacking will not be able to grab you if you maintain a slight distance (between you and it). If it tries to turn and grab you, a simple retreat will allow you to escape!