Reimaging a workstation

I’m rolled out an image to new Workstations. Its work fine. The ws connects the zoneserver. The ws were the image drawn I prepared as wrote. Now I change the configuration of the ws and I created a new image. I associated the new image to the old ws. After reimageing, the ws not connected the zoneserver. The ws-old-name selected from the image safe data. Its OK. But I must execute the zac command to unregister ws from local and register it to the zone. But now the ws is corresponding with the zoneserve. Where is the error?? I would, that the new image is immediately usable.

Sorry for my bad English

Thanks toni