how to monitor three mysql instances that are in the same linux server?

Hi all
I hava three mysql instances in the same linux server, and the mysql ports are 3306,4589 and 3976.
Following the official document, I have monitored the mysql server in the default port with Percona Monitoring Plugins for Zabbix in the zabbix server.
My quetion is how to monitor the other mysql instances which ports are 4589 and 3976?
The mysql Server version is 5.6.22.
The linux Server version is Red Hat Enterprise Linux Server release 5.8 (Tikanga).

Any advice or perhaps a working example would be much appreciated.
Many thanks