Although you add the ZMD and E460 meters both as a Landis & Gyr DLMS meter, the OBIS codes, DLMS login mechanisms etc. are different, so a core way we know which methodology to use, is to look at the length of the serial number entered.

ZMDs must be 8 or 13 digits, and E460s must be 11 digits, regardless of how many phases it uses.