Firstly, there is a list of Endnote styles for specific journals at http://www.endnote.com/support/enstyles.asp. Would it be possible to import those styles into Zotero? If this is not an option (copyright or some other reason),
would it be possible to create and customize a new citation style in Zotero? And then mail it in as a contribution? I figure if this could be a community effort we could all help each other.
There are thousands of different styles, and even though they may all be based on a few key styles, they are all slightly different. Which is why this discussion is so long.
An EndNote style (.ens file) import function as proposed by someone early on in this discussion might be hard to develop, but would make a huge difference! I would migrate to zotero straight away if this was available. And in the long run it would safe a lot of time for the developers, too.