I had a similar problem with MySQL and Java not starting after tweaking some of the
performance tuning parameters - namely the
mysql_memory_percent and
mailboxd_java_heap_memory_percent - which are set at 30 and 40 respectively on your setup. I remember the
network stack settings confused it a bit too.
How much RAM does the server have and what is the usage like on the box before you try to start zimbra? (Run
free -m).