Developing plug-ins for Zimbra Desktop?

[TheOrbix]

Hello, is it possible to develop custom plug-ins for Zimbra Desktop, to extend and customize the application features?
I have a customer that would like to integrate Zimbra Desktop with an open source ECM platform (Alfresco Enterprise), in order to store in the Alfresco Repository the content of messages and attachments.
This almost certainly requires the implementation of a customization of the Zimbra Desktop client application.
I know this would not be a problem for other email clients that can be extended via custom plug-ins (like Thunderbird), but I don't know if Zimbra Desktop provides the same capability.