You can do this with the Crop effect, which has a Zoom setting.
Video effects > Transform > Crop - drag this onto your photo.
Then in the crop effect control, set a keyframe where you want the zoom to start for each of the top / bottom / left / right directions, set another keyframe where you want it to end, check the Zoom checkbox and then on the last keyframe, set the crop amounts for each direction.
I don't understand what you're trying to do. if you zoom in to the picture you will enlarge it. that's what zooming in means to me (bwdik). maybe draw a couple of frames and take a picture of them on your phone to illustrate what you want to do...