I would like to suggest KDETools Zimbra to Outlook Converter that will help you with an easy and fast tool to import Zimbra to Outlook.
Some features are:
The application directly import Zimbra file to Exchange Server and Office 365 account
There is no file size Limitation.
The application also supports different types of file formats such as PST, EML, MBOX, NSF, OLM, PDF, EMLX, HTML, and etc.
Read More:  https://www.kdetools.com/zimbra/