Opening Pan /Crop and making the frame smaller means you have zoomed in. Play with it and watch Preview.
To do it over time, use a keyframe at the point you wish to arrive at the fully zoomed in state. This will animate from Unzoomed to Zoomed.
There is much more this tool can do, but start with that and see how you go.
Peter Wright
Perth, Western Oz
http://www.allroundvision.com.au