Couldn’t be simpler. With Premiere, you simply set a keyframe marking the scale at over 100 percent. Move the scrubber a second or two on, set a scale keyframe for 100% - or whatever size you want. Over the time period, the size will change.

If you don’t want the zoom from the centre, keyframe the position parameters as well - it’s very easy. Play with it, you'll see how it works.