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?