The "void" means the RFID inlay was not detected by the RFID reader on the printer. Here is why.
When reading RFID tag from ZT410 panel, it's an immediate read. When reading RFID tag from ZPL, the reading becomes a part of the ZPL that defines a label. This means that the printer needs to know where the RFID inlay is placed on the label, so that it can correctly activate the reader when the RFID inlay is fed to the RFID reader on the printer. In order for the printer to know the inlay position on the label correctly, it is required to do a RFID calibration following the label calibration on the printer. After the calibrations are done, the above ZPL should return the correct tag ID data from the reader.