How do i make a map changer for a zombie game?

first you can put the models of your maps in the Replicated Storage, i didnt play the game you mentioned, but lets say you have a gui to vote for the next map, when the next map will spawn in you can use something like this :

local map1 = game.ReplicatedStorage.Maps.Map1:Clone() -- "Maps" would be a file where you put in the "maps" models and "Map1" would be the name of the map used
map1.Parent = game.Workspace  -- this will make the map clone into the Workspace there you can have spawn points on the map to teleport players to depending how you want to do it

for more help well i wont make the script for you but i guess i can help on some things if this isnt enough