Zenoss Core provides several ways for us to extend the base functionality:
We install and configure a Nagios plugin in Chapter 5, Custom Monitoring Templates.
The information presented there will be valuable for those of you who want to develop your own plugins.
The ZenPack architecture allows us to package plugins and configurations for distribution to other users and the community at-large. Chapter 9, Extending Zenoss Core with ZenPacks walks you through the steps of installing a community ZenPack, and how to create your own ZenPack as well.