In addition to pyzor & razor what else do you have set?
To cut down on emails to addresses you don't even have, you might also change the entry in /opt/zimbra/conf/zmmta.cf for smtpd_reject_unlisted_recipients to 'yes', save the file and restart postfix. (postfix reload)
You do any realtime blacklists? (Just remembered that their in a different doc than the improving anti-spam one.)
sbl.spamhaus.org (or zen.spamhaus.org contains 3 lists)
you can enable them by:
I also use dnsblcount to get some totals - nothing fancy on those summaries, but makes you feel like something's being done!
zmprov mcf +zimbraMtaRestriction "reject_rbl_client bl.spamcop.net"
Graylisting (I'm a fan) Graylisting - Improving Anti-spam system - Zimbra :: Wiki
-careful with reject_unknown_client & reject_unknown_hostname as they can block more than you think sometimes...
Occasionally your ALW might need a kick if you got off on the wrong foot or something: Correcting poisoned Auto-Whitelist (AWL)
zmprov mcf +zimbraMtaRestriction reject_invalid_hostname