1.On the layers palette, select a layer which should scroll/zoom "slower" (usualy on right of screen, if not turn it on via the ribbon bar in the home tab)
2.look to the left and you'll see layer properties; use these to change scroll speeds (tip: only change the ones which end in "Rate" for what you want to do) try putting one at 50, another at 25 etc.
hope that helped.