Here’s one way of doing it. Assuming two images, place each image on a separate track. For each image, create your zoom from small to large keeping image centered. When you open the pan/crop window for each image, make sure you set the pan/crop preset to your project size (16×9 usually), not default. Once you are satisfied with the motion of each image that is centered, use track motion to position each image to the right or left of center, or wherever you want it. In other words, its a two-step process. First, create your zoom in the pan/crop window and second, position the image using track motion. Hope this helps.
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Here a couple of screenshots to help. First, the pan/crop window at keyframe one, then at keyframe 2.

