hokuto shinken would be effective in a post nuclear world as far as i know
I don't know about what style but I'd be thinking front kick to chest to knock them over, elbow to jaw (can't bite with broken jaw) if too close or a simple hip toss to get them on the ground.
If there are two of you then one person knocks the zombie over with a hand log splitter (hammer end) second person pins zombie down with another log splitter and first person reverses log splitter and buries it in the zombies head.
This is for slow-moving zombies, for fast zombies I'd recommend hiding, a toyota land cruiser with full fuel tank and a L1A1 SLR (with scope) and plenty of rounds.
I think that Muay Thai is the best MA for zombie apocalypse. Why? Reason is simple: It's claimed to be the best standup MA, so you can elbow, knee and finally stomp kick the zombie so he won't get up. Besides this, i don't think that zombies would try to grapple you.
Jusy my thought.
Anything with "alive training" will end with your brain being eaten.
Go for "dead training". Lots of it out there.
Dord Fighting System, without a doubt. I hear the leader is actually working on a manual to deal with THIS EXACT PROBLEM.