Zenoss allows you to export a list of your devices to an XML file for easy importing into another Zenoss instance. From the command line, use the command:

zendevicedump -o mydevicelist.xml

This will dump the names of your devices, including their device classes, groups, systems etc. to a file called mydevicelist.xml.

To load these devices into another Zenoss instance (or reload them into the same instance), while in the Zenoss instance where you want the devices to be discovered, run the command:

zendeviceload -i mydevicelist.xml

Zenoss will then attempt to discover each of the devices in the XML file.