There are multiple third party tools available on the internet; you just go with the right solution and that is Vartika Zimbra to PSTConverter tool when I required same issue and got accurate result. You can export Zimbra Mailbox between components like emails, calendars, tasks, notes and briefcase. It is a Windows utility, supports Wins 10/8 / 8.1 / 7. This Software also gives you free demo versions which you can export 30 email per folders.
Export PST to an outlook from Zimbra Emails
Select the file tab and choose Open & Export.
Select the Import/Export tab. Import and Export Wizard will appear. ...
Then select the Outlook data file option.
Select the Zimbra backup files folder.
Click the Browse button to save the file.
Check the PST file where you saved it.