As you can see, custom device reports make writing custom reports in Zenoss Core tolerable. It keeps us from pulling our hair out while trying to write complicated scripts from scratch. If, however, you want to write your own scripts from scratch, the Zenoss Core Administrators Guide provides a brief introduction. And with this chapter as background information, you should at least have a good starting position.
That concludes our introduction to Zenoss Core. Now, go forth and monitor.