Slowing down time

Hi guys.

My objective is to Zoom in to a location on a map but the problem is that I only have 6 frames (6 shots of the map with the different scales) When I play the animation the map zooms in so fast that it’s frightning! If I add more frames or slow down the frame rate then the animation becomes jercky. Does anyone know of a way thay I can slow down the animation within the 6 frames keeping a smoothness?