Zen Cart multiple picture product admin/upload

Need to modify the existing Zen Cart product admin page to allow multiple photo upload (currently only one photo allowed). The modification must be user friendly, i.e. all UI based (no off page procedures or other funny stuff) and easily operated by an avg end user. Attached "zen cart [login to view URL]" of the existing photo attachement section of product upload for reference Attached "zen cart [login to view URL]" is the modification that I need (or similar if can be better) Requirements: 1. Max 4 photo upload 2. auto photo size conversion bound to 640 x 640 image at max when upload 3. existing photo file name in used must be shown when editing product detail 4. must allow photo replacement or deletion for uploaded photo 5. all 4 photo upload slot must be accessible at insert and editi mode. Tech spec - Zen Cart v.1.3.9b - Hosted service at [login to view URL]