Thanks for your reply. I was able to go a little farther. Now it failed at this point:
----------------------------------------------------------
Removing existing packages
zimbra-core...done
Removing deployed webapp directories
Removing /opt/zimbra
Installing packages
zimbra-core......zimbra-core_5.0.0_GA_1869.UBUNTU6_i386.deb...FAILED
###ERROR###
zimbra-core_5.0.0_GA_1869.UBUNTU6_i386.deb installation failed
Installation cancelled
root@zimbra:~/Desktop/zcs-5.0.0_GA_1869.UBUNTU6.20071218195304#