At last a work-around to get Zimbra to run on my Vista64x machine. Using information that I found in this forum I created 2 batch files and placed them on my Desktop. Each file has one command.
Batch #1: "C:\Program Files (x86)\Zimbra\Zimbra Desktop\win32\zdesktop.exe" "C:\Users\<my name here>\AppData\Local\Zimbra\Zimbra Desktop\conf\zdesktop.conf"
Batch #2: "C:\Program Files (x86)\Zimbra\Zimbra Desktop\win32\zdrun.vbs"
After running these files in order, Zimbra will run. So far no problem. BTW, when I placed both commands in a single batch file, the second command would not run.
To repeat: I never had any problem running Zimbra on my Vista 32x or my Windows 7 64x.
Even with this work-around, I prefer Zimbra over Outlook 2010 which gives really crummy mail notifications.