How do you call two functions at the same time?

I've tried using a coroutine, this to be exactly...

coroutine.resume(coroutine.create(leftFlash,rightFlash))
~~~~~~~~~~~~~~~~

...however, only one function executes, and it goes on forever.
In case you need the functions, here they are:
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function leftFlash()
			repeat
			local i = 0
			game.Workspace.G12.Transparency = 0
			game.Workspace.G12.Light.Enabled = true
			game.Workspace.G12.Light2.Enabled = true
			wait(.25)
			game.Workspace.G12.Transparency = 0.5
			game.Workspace.G12.Light.Enabled = false
			game.Workspace.G12.Light2.Enabled = false
			wait(.25)
			i = i + .5
			until
			i == 5
		end
		function rightFlash()
			repeat
			local i = 0
			game.Workspace.G1.Transparency = 0
			game.Workspace.G1.Light.Enabled = true
			game.Workspace.G1.Light2.Enabled = true
			wait(.125)
			game.Workspace.G1.Transparency = 0.5
			game.Workspace.G1.Light.Enabled = false
			game.Workspace.G1.Light2.Enabled = false
			wait(.125)
			i = i + .25
			until
			i == 5
		end