The function RemoveMG does not exist in maps/mp/gametypes/_weapons.gsc. And that is why the mod doesn't work.
You can do now two things:
Comment the line 'thread maps\mp\gametypes\_weapons::RemoveMG();' in zom.gsc by adding // in front of it.
Or you can find the function and add it or make the function.
The function that you are probably missing is this. But it is moved to _weapons and renamed to RemoveMG.