Haha.. Games are becoming more interesting by the day !
I love the idea where we need to chip some tokens and fight for survival.

You will need a bigger map because many more player will start to join and this game might become a lot popular soon.

If first to reach = winner, then I suggest a rule where player needs to fight in the same square. If there is a zombie in the square along with two players, then the players will have a peace treaty for that round and they will attack the zombie to clear it out..

Peace treaty will not end until the zombie is dead. I ask for 2 turns each round.
No one will be safe in this case.