This addon allows you to override the incompatibility warnings: Nightly Tester Tools :: Add-ons for Firefox Of course that doesn't actually make it compatible if there really is an issue, but it looks like 3.6.3 is just a security patch so it could be fine.
3.0a3 is marked as compatible with 3.6 via its update manifest on the Zotero server. If you have add-on update checking enabled, it should install fine.
Of course that doesn't actually make it compatible if there really is an issue, but it looks like 3.6.3 is just a security patch so it could be fine.
Thanks