One of the missing requirements was the Zimbra off-line desktop (mail) client, which is not available in x86_64. This is what you need to install on cross libraries to get the standard install script to work for Zinbra:
$ sudo yum install libXext*.i386 glibc*.i686 libstdc++*.i386 xulrunner.i386
After these install, you can just run the install script as follows:
# This was the latest version for Linux at the time. # $ sh zdesktop_1_0_build_1593_linux_i686.sh