I wrote a Zotero extension many years ago when doing my PhD[1]. Unfortunately, recent changes have broken it, I can't figure out what's wrong (XUL is not exactly well-documented these days), and the developers aren't responsive[2]. :(

[1] http://mackerron.com/zot2bib/

[2] https://groups.google.com/forum/#!topic/zotero-dev/a1IPUJ2m_...