SOLUTION:
JezuzLizard said in Error finding maps when trying to run custom zombies maps:
fireeyeeian
This is the syntax you have to use
set sv_mapRotation "loadmod \"mods/dead_ship\" map dead_ship loadmod \"mods/nazi_zombie_Relic\""
You'll also need to setup fastdl for players without the mods to be able to join the server
https://plutonium.pw/docs/server/t4/fastdl/#setting-up-fastdl
My problem:
I followed the guide at https://plutonium.pw/docs/server/t4/loading-mods/ but when i start the server I see
Error: Can't find map "dust2".
A mod is required for custom maps

The custom maps are located in: "%localappdata%\Plutonium\storage\t4\mods"

I also set "set mod="mods/mp_custommaps" in the .bat as I have no mods just maps

The server works 100% fine with no mods/maps but when trying to run custom maps it gives the error and never successfully heartbeats.
PS: the screenshots show that the dust2 name has a lowercase "d" instead of an uppercase "D" like in the folder. I fixed that but that didn't fix the error.