That's a trivial thing, but I observed that termination of zabbix_server daemon causes an "Aborted_clients" mysql variable growing.
Looks like zabbix does not close MySQL connection properly.
Yes, that's a minor but may be would be more nice to handle that cleanly.
Try to watch on these variables before and after daemon termination:
When login and logout using "mysql" or refresh a frontend page (Apache+PHP as a client) it does not grow.