How to hunt lv.6 zombie to activate chester?

What I Did was a level 1-5 Zombie attack once, then attacked a level 6 multiple times (It's random...not every battle, I also noticed you have a chance of getting Chester on level 5, but I got Him on a level 6) keep hitting and you will get him.

Once completed Level 6, go to the Heroes tab and Chester should appear

Every time you defeat a Level 6 Zombie it "MAY" drop a Chester Frag. You need 10 Frags to recruit Chester. So you may need to defeat 15-20 Level 6 Nurse Zombies to get chester.

On the world map there are zombies to attack (not the zombie lairs). You attack the normal zombies by yourself. Use the search option (magnifying glass icon) to find one of the level you want.

To attack a level 6 zombie you will need to have already defeated a level 5, and before that a level 4 and so on.