When I restart zimbra or run "/etc/init.d/zimbra status" there is no output.

This can easily be fixed by changing this:
su - zimbra -c "zmcontrol $1 </dev/null >>/opt/zimbra/log/startup.log 2>&1"
to this:
su - zimbra -c "zmcontrol $1 </dev/null 2>&1 | tee -a /opt/zimbra/log/startup.log"