Spawning waves of zombies, but function keeps repeating Wave 1?

--Its quite simple to do what you want, but there are a few things you need to learn as well. Please read all my --'s and learn from them.
local tZombie = game:GetService("ServerStorage").Zombie1
local zCnt = 0
local rnd = Random.new()
local wave = 1 -- We'll use this to determine what wave we are on

local function spawnZombies() -- A function is something that will run the code inside the function whenever you call it. There is no reason to have multiple instances of the same function that do the same thing. Simply define the function once, and anytime you need to use it call it.
	for i= -1118, 8, 230 do  --Why are you setting this up like this? i= # means what value i starts at. The second number is what it increases by, and the third is what it stops at. You want 168 zombies to spawn?    i = 1, 1, 168
		local zombie = tZombie:Clone()
		zombie.Parent = workspace.Zombies
		local xLoc = rnd:NextInteger(-75,10) 
		local zLoc = rnd:NextInteger(-75,10)
		local pos = Vector3.new(xLoc, 3, zLoc)
		zombie:MoveTo(pos)
	end
end

local function getZCount()
	local num = #workspace.Zombies:GetChildren() 
	return num
end

-- Like I said, you only need one function to do everything. If you want values to change you still don't need another function, just add arguements to it like the following example:
--[[
Example function

local function spawnZombies(zombiestospawn, xLoc1,xLoc2,zLoc1,zLoc2)
	for i= 1, 1, zombiestospawn do
		local zombie = tZombie:Clone()
		zombie.Parent = workspace.Zombies
		local xLoc = rnd:NextInteger(xLoc1,xLoc2) 
		local zLoc = rnd:NextInteger(zLoc1,zLoc2)
		local pos = Vector3.new(xLoc, 3, zLoc)
		zombie:MoveTo(pos)
	end
end
]]
workspace.Zombie.ChildRemoved:Connect(function() -- Instead of running a loop to check how many zombies are left, just check to see when one was removed from the zombie storage folder.
	zCnt = getZCount()
	if zCnt < 20 then -- If zombies count is less than 20, start next wave
		wave = wave + 1
		print("Spawning Zombies Wave ".. wave)
		spawnZombies()
	end
end)