What installation document are you following ? Have you read through this ?
http://www.zimbra.com/docs/os/latest...erver_install/
What O/S are you running ?
You do need MTA and LDAP installed for it to run. Port conflicts could be either when you de-installed and re-installed ZCS some old processes were still running, or the O/S has installed a MTA or LDAP server.
So, shutdown ZCS and then remove it. Then make sure no old processes are running under the zimbra user. Then check that no other MTA or LDAP is running. You can use netstat -an to see if a port is open.
We can help but please help us to help you
