The Zimlet gallery is the best place to find and publish extensions for Zimbra.
Product News – Seafile Official Blog
Blog – Page 3 – Zeta Alliance
WebDAV - Zimbra :: Tech Center
Zimbra ownCloud Extension Zimlet
ZetaHub
Zeta Alliance · GitHub
Nextcloud – Zeta Alliance
Zimbra ownCloud Extension Zimlet
Dns Big, PDF, Computer Mediated Communication
GitHub - Zimbra-Community/owncloud-zimlet: Integrate Nextcloud
WebDAV - Zimbra :: Tech Center
WebDAV - Zimbra :: Tech Center