I have recently posted a workaround here:
[SOLVED] Zimbra Desktop 2
that I think solves in an elegant manner the "Could not read override.ini" error.
If you are trying my hack in the same machine as the one that had this error you should do step 2 (registry delete) and step 3 (Data program delete) compulsory.
After finding that my hack does work I would be very pleased that you report your experience (including Windows version and language) at the bug:
so that Zimbra developers can actually check if it is working or not and hopefully decide to include it in the next Zimbra Desktop release with maybe some release notes about step 2 (registry delete) and step 3 (Data program delete) being compulsory in some situations.
Thank you very much for your attention!