How would I change two variables in a loop where one counts up and the other counts down?

So I'm working on a GUI and I'm working on a little cutscene in it. I'm making textlabels change transparency within a loop. I want to trigger another loop without stopping the present one and/or change two different variables in the same loop where one counts up and the other counts down.

This is what I have now.

function onPlayerAdded()
	local intro = menus.Intro
	intro.Visible = true
	local tew = intro["TEW"]
	local presents = intro.Presents
	intro.BackgroundTransparency = 0



	for i = 1, 0, -0.1 do --First loop 
		tew.TextTransparency = i
		wait(0.1)
	end
	
	for p = 1, 0, -0.1 do --Second loop
		presents.TextTransparency = p
		wait(0.1)
	end

end

Players.PlayerAdded:Connect(onPlayerAdded)

How would I change two variables in the same loop where one goes up and the other goes down? This was my attempts at figuring it out.

--Attempt 1
for p = 1, 0, -0.1 do --Second loop
	presents.TextTransparency = p
	wait(0.1)
	tew.TextTransparency = -p
end

--Attemp2
while tew.TextTransparency ~= 0 do
	tew.TextTransparency = tew.TextTransparency - 0.1
	wait(0.1)
end

if tew.TextTransparency == 0 then
	while presents.TextTransparency ~= 0 do
		presents.TextTransparency = presents.TextTransparency - 0.1
		tew.TextTransparency = tew.TextTransparency - 0.1
		wait(0.1)
	end
end

I'm out of ideas from here. What should I do?