How can I call multiple objects in a tween?

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I have a script where I’m wanting all the parts inside of a group to change transparency in a tween. The problem is, you can’t do that, and you can’t union them together. How can I do this?
Script: (PartsInside is the objects I want to call)

local showText = game.TweenService:Create(workspace.Appearance.PartsInside, tweenInfo, {Transparency = 1})
local hideText = game.TweenService:Create(workspace.Appearance.PartsInside, tweenInfo, {Transparency = 0})