As a former Gallery 2 user, I can confirm that the file structure is similar to that of Zenphoto. There might be a few minor differences, especially with regard with non-pure-ASCII characters (which should be avoided anyways).
So if you own that domain, it should be very easy to move the photos en masse from the Gallery folder to the zenphoto "albums" folder. And because Zenphoto recognizes the structure of the album, you will get the skeleton of your gallery without further intervention.