I was installing an old zimbra (5.0.19) on an old CentOS 4.7, when I got this error during installation:

Install zimbra-convertd [Y] N
Checking required space for zimbra-core
checking space for zimbra-store        
df: `/opt/zimbra': No such file or directory
./util/utilfunc.sh: line 557: / 1048576: syntax error: operand expected (error token is "/ 1048576")

Removing /opt/zimbra
Removing zimbra crontab entry...done.
Cleaning up zimbra init scripts...done.
Cleaning up /etc/ld.so.conf...done.    
Cleaning up /etc/prelink.conf...done.  
Cleaning up /etc/security/limits.conf...done.

Finished removing Zimbra Collaboration Suite.

Installing packages

./util/utilfunc.sh: line 564: /opt/zimbra/.install_history: No such file or directory
this server is a vm freshly installed.

The installation continued without any other issue.
The other minor thing i noted, was that it do not asked me to notify zimbra ppl for this new installation, or not.