Its pretty simple :p but i doubt anyone will help anyone with this lol, if you have the source of the menu and source of the game mode, it should be pretty easy to do...
There are zombieland gamemodes with host menus, but I don't think very much can be added to the menus when you have a gamemode loaded without it causing a syntax/overflow and freezing your game. Maybe it'd be possible to find the source to one of the zombieland game modes that have a host menu and editing it.