one of the file is in:

includes>modules>your_templates_folder>additional_images.php


what I did was open them both and compared the files then when I came across the zenbox cod I copied it to the IH2 file....saved then reuploaded it to the folder on the server.

remember to work off a copy of the file NOT the original and I try to put a ~ at the end of the original ones name [additional_images.php~] on the server to have it there should the edited one misbehave the I just remove the ~ after deleteing the edited one...that way I don't kill my store too much