How can i use math.random() to spawn different types of zombies in my zombie game?

For my zombie game i need to make different types of zombies so the game does not get too easy. Also if its possible, config how rare the zombies are. Here is the script : ~~~~~~~~~~~~~~~~~

local CS = game:getService("CollectionService")

while true do
    wait(5)
    for i, v in pairs(CS:GetTagged("spawner")) do
        if game.ReplicatedStorage.Values.gameInProgress.Value == true then
            if game.ReplicatedStorage.Values.zombiesRemaining.Value > 0 then
                local NPC = game.ReplicatedStorage.Zombie:Clone()
                NPC.Parent = v
                NPC.HumanoidRootPart.CFrame = v.CFrame
                CS:AddTag(NPC, "Zombie")
                game.ReplicatedStorage.Values.zombiesRemaining.Value = game.ReplicatedStorage.Values.zombiesRemaining.Value - 1
            end
        end
    end
end

~~~~~~~~~~~~~~~~~ What i want is different types of zombies spawning using math.random() also when replying how to do it i need the position.

EDIT: If there are any other ways i can do the other types of zombies and its shorter, ill accept.