To localize Zotero, please register yourself at [[http://www.babelzilla.org|BabelZilla]].  Search for "zotero" and choose a locale for which you would like to translate.  BabelZilla will allow you to edit all localizable strings online except for those contained in the locales.xml file.  To edit locales.xml, download the file and take the following steps:

1. Open the file in your favorite text editor as a unicode (UTF-8) file.

2. Make the necessary changes to all text in between the XML tags, i.e. everything that is like >text< not the code that is like <term>.

3. Save the file as UTF-8 and upload back to BabelZilla.