We have a single image for all devices with Zenworks is included in the image.

There are a some devices that should not be managed by Zenworks at all.
How can I ensure this is the case? I don't want these devices to register.

If I have the service disabled, then there are EXTREMELY slow logins (presuming something is timing out?).
If we enable the service, it registers in the zone and gets a bunch of settings etc that we don't want.
It seems overkill to allow it to register to the zone, then unregister it.

Note - Disable passive login, etc, doesnt' cut it as we don't want any workstation assigned items being pushed through, and we don't want any WS objects seen in the zone.
These devices will mostly be off the network once imaged - they are not on the domain.

Any advice?
As said, disabling the Zenworks service gives a REALLY slow login for local users. I'm happy to disable the service if we can combat the slow login issue.