Warning, this is a horrific security hazard, never do this on a production server, or on a server in a production network that you care about the data contained withinWhen I was playing around with this, I eventually gave the zimbra user root privilages with a line in the suders file as:
zimbra ALL=(ALL) ALL
This is not a good idea
Nothing went wrong as a result, and it did get passed the erronuous password issues, but there's always a risk running as root and I dont recommend you do it at all!
That said, it did help me to get past the problem, and if you are in a VM with good backups, you may be comfortable trying this.