Jon,
I have recently had to do this same procedure for our brocade devices. To start, I would turn on debug for your syslog daemon (zensyslog debug) and find the actual message your zensyslog.log - it should look something like this "
2013-06-12 11:58:18,988 INFO zen.Syslog: No matching parser: 'xx.xx.xx.xx LB-HO-INT-T1, L4 server 1.1.1.1 web1 port 443 is down due to healthcheck'" with the no matching parser message in the line
If you post that back here, i can show you how to write the regex if you want.
--Rob