We will use Radmin VPN for this tutorial as it is the most stable for cracked games.
Legitimate Project Zomboid uses:
Cracked versions remove the authentication check but break the relay system. Therefore, you must simulate a Local Area Network (LAN) over the internet using a VPN (like Radmin VPN, Hamachi, or ZeroTier). how to play multiplayer in crack installed project zomboid
If you are in the same house, you don't need extra software. We will use Radmin VPN for this tutorial