before you talk about techniques you need to know the zombie rules. you can find the list of rules here http://www.zombielandrules.com/
since zombies don't feel pain, therefore, all those pain compliant techniques won't work. empty hand techniques would just delay the inevitable of you get eaten. so break out the shiken and go to town. don't forget the double tap rule. you see this problem in many movies when folks don't follow the double tap rule, and ended up with the bad guys getting up and shoot you in the back. of course aikido folks will get eaten first, because of the harmony and loving toward your attacker attitude.