I do know the game says Co-op and multiplayer, but could someone give some more information on this? Do you require gog galaxy for the Multiplayer?

It's NOT required. The host needs to open the ports 16261, 8766, 8767 in order to create a game where people can join. You create a world with tons of options and people can join (optional password too). It may be listed in the public servers if you wish.

You can play with people that uses the Steam version and mods, however, you will need to manage manually the mods (it's not difficult, just download, place them on the mod folder, and enable them in the host & clients). If the host owns a Steam version, they need to start the game with -nosteam parameter.

Note: you need to whitelist in your firewall the project zomboid exe AND the java.exe that you will find inside PZ folder

Thank You for the information!

Hello friend, I need detailed help to create a server to play with friends. I've had the game for a month now, and until today, I haven't been able to achieve it. It would be a huge favor if you could provide me with step-by-step instructions. I've searched in many places, and you are my last hope. Save me, Obi Wan Kenobi.

Hi,

Each router is different unfortunately. I may assist you to open the ports, ie, using Discord. Are you going to play with other Steam players? or only GOG players? If you want add me as friend and we can chat when both of us are available and do things faster.