Hi,
you can run a script
#!/usr/bin/env python
import Globals
from Products.ZenUtils.ZenScriptBase import ZenScriptBase
from transaction import commit
dmd = ZenScriptBase(connect=True).dmd
for dev in dmd.Devices.getSubDevices():
print dev.id
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However, this may be very slow and I would suggest using the REST api (cfr. http://docs.huihoo.com/zenoss/dev-guide/2.1/ch03s01.html )
e.g.