Well, the problem is you said you had the same problem as the o/p - his first post was a DNS problem. You appear to have two different problems, first you are missing a shared library - search the forums for libexpat.so.1 and you'll find the answer.
The second problem is LDAP, did you get any erros during the install (check your install logs)? You can also check your DNS by running the following (on the zimbra server):
and post the output.
host `hostname` <-- type as-is and use backticks not single quotes
dig yourdomain.com mx
dig yourdomain.com any
You can also try the LDAP troubleshooting tips form the wiki.