1: Set up.

Firstly I want you to open up the games prefix folder, this is located in your steam library folder, the path should look something like this "SteamLibrary/steamapps/compatdata/10090/pfx/drive_c/users/steamuser/AppData/Local/"

this folder is where call of duty world at war stores information about its self and mods, leave this folder open for now we will go back into it later.

2: starting the installer for the custom zombies installer.

First make sure you have wine installed, we will use wine to allow the mod.exe to launch, "Wine Is Not an Emulator" it is a compatibility layer, pretty much translating it to linux code, if you search in your package manager wine should be available.

Now press the custom zombies exe file and if wine is installed this should pop up, click next until it tells you to find the game directory.
should look like this.

Now find your game directory which should be located in your steam library folder, the path will look like this "SteamLibrary/steamapps/common/Call of Duty World at War/"

now finish the installer and it should be installed BUT WAIT the installer didnt install it in the correct place, so if you start the game you will see the mod isnt installed, dont worry I know what happened.

3: Putting the mod in the correct directory.

Open up your home folder, and go into your user folder, should look like this "/home/YOURNAME/" and now on the top path bar type ".wine" and press enter to go into the folder and now go to this path "/home/USERNAME/.wine/drive_c/users/USERNAME/AppData/Local/" in this folder you should see an activision folder which means the mods installed correctly but not in the right place now copy that folder and lets go back into the other folder we opened at the beginning of the guide and paste the activision folder into that folder, now we have the mods installed if you start the game it should be installed correctly!