Hi
If you use the POSITION effect with your green screened image (placed on the overlay track) you can animate its movement around the screen using keyframes, setting the position between frames either by appearance in the preview pane or by position set as figures in the Horizontal and Vertical boxes. The image will move smoothly between the keyframe positions over the underlying main track clip
.If you then also combine the SCALE effect the the overlay, the moving image/clip can also be enlarged or reduced in size (in effect be zoomed in or out) again either by the preview appearance or by entering the number values into the scale value boxes.
As an example. this is a screenshot of the interface with a yellow bouncing ball (the image of a yellow circle on a green background; greenscreened to remove the background colour...but it could be a clip) changing in size (zooming) as it bounces around the background clip.

It uses just POSITION and SCALE
Nat