When I went to the library site via Google, I had no problems using the Franklin library catalogue with Zotero. The "Library (Voyager)" translator should appear in the address bar if you're looking at the search page or an entry.

When I follow the link posted above, the translator does not recognize the website. I'm not sure exactly why this is, but as far as I can tell, as long as you start your search from http://www.franklin.library.upenn.edu/ you shouldn't have a problem.

The book bag feature appears to be password protected and only for use by University Pennsylvania staff and students, so I can't look into if Zotero might work with that site. You can, however, just save items to Zotero rather than save them to your book bag, and the outcome should be the same.