How much to get infinite scroll to work on this theme?
http://www.zenphoto.org/theme/zpBootstrap/index-normal-size.jpg.html

Working example here:
http://www.zenphoto.org/theme/zpMasonry/zpMasonry-news.jpg.html

Plugin used in working example.
http://www.infinite-scroll.com/

I suggest to contact the developer of the theme himself as he is most familiar with it.

Otherwise please use the "paid support" page.