I only want left mouse and right mouse to zoom, how can I fix this?

Why does every button I press zoom In? I only want it to zoom when I click the left mouse and the right mouse. This is a camera script I am using:

local userInputService = game:GetService("UserInputService")
local runService = game:GetService("RunService")

--Player & Character
local localPlayer = game:GetService("Players").LocalPlayer

--Other
local Camera = game:GetService("Workspace").CurrentCamera
Camera.FieldOfView = 90
--------------
--- VALUES ---
--------------

local xAngle = 0
local yAngle = 0
local cameraPos = Vector3.new(3.5,0,7.5)

----------------------
--- INITIALIZATION ---
----------------------

wait(0.01)
Camera.CameraType = Enum.CameraType.Scriptable
userInputService.MouseBehavior = Enum.MouseBehavior.LockCenter

-----------------
--- FUNCTIONS ---
-----------------

userInputService.InputChanged:Connect(function(input)
	if input.UserInputType == Enum.UserInputType.MouseMovement then
		xAngle = xAngle-input.Delta.x*0.4
		--Clamp the vertical axis so it doesn't go upside down or glitch.
		yAngle = math.clamp(yAngle-input.Delta.y*0.4,-80,80)
	end
end)

runService.RenderStepped:Connect(function()
	local Character = localPlayer.Character
	local rootPart = Character:FindFirstChild("HumanoidRootPart")
	if Character and rootPart then
		--Set rotated start cframe inside head
		local startCFrame = CFrame.new((rootPart.CFrame.p + Vector3.new(0,2,0)))*CFrame.Angles(0, math.rad(xAngle), 0)*CFrame.Angles(math.rad(yAngle), 0, 0)
		
		--Set camera focus and cframe
		local cameraCFrame = startCFrame + startCFrame:vectorToWorldSpace(Vector3.new(cameraPos.X,cameraPos.Y,cameraPos.Z))
		local cameraFocus = startCFrame + startCFrame:vectorToWorldSpace(Vector3.new(cameraPos.X,cameraPos.Y,-50000))
		
		Camera.CFrame = CFrame.new(cameraCFrame.p,cameraFocus.p)
		
	end
end)
---------------------
--- ZOOM ---
----------------------

userInputService.InputBegan:Connect(function(input)
	if input.UserInputType == Enum.UserInputType.MouseButton1 or Enum.UserInputType.MouseButton3 then
		cameraPos = Vector3.new (2,0,5.5)
	end
end)

userInputService.InputEnded:Connect(function(input)
	if input.UserInputType == Enum.UserInputType.MouseButton1 or Enum.UserInputType.MouseButton3 then
		cameraPos = Vector3.new (3.5,0,7.5)
	end
end)