Follow these steps;
1) First off you’ll need to have Notepad++ or some other text editor that allows you to make a .cfg file.
2) Go to Steam\SteamApps\common\State of Decay\Game
3) Create the System.cfg file with the following codes inside it.
zm_disableNPCTargeting = 1
zm_showInfestations = 1
zm_playerInvisible = 1
pl_infinite_health = 1
pl_infinite_stamina = 1
4) Launch the game, you will be invincible and invisible (mostly… Freaks can still see you).