If a device on which FRP is enabled, needs to be unenrolled from the zone, then to remove the FRP data from the device as well as from the ZENworks database, you need select the Wipe Factory Reset Protection data option while initiating the Unenroll quick task. For more information on this quick task, see Unenrolling Devices.
If the device has already unenrolled and is deleted from the zone and if the FRP data is not wiped during unenrollment, then you can execute the zman mfpr command to remove the FRP data for these devices from the ZENworks database. These details will be removed only from the database and not from the device. Therefore, before running this command, it is recommended that you run the zman mfetf command to take a backup of the FRP details.