Sorry Barry, I don't have any listing for a 'BZ' engine number in any VW reference. The ETKA parts DVD does not list it.
In fact the 'B' 1600 engine mentioned above is the ONLY 'B' prefix Volkswagen engine.
As for the Z, there are a few VW engines with that letter:
'1Z' is a 67 kW 1900cc Golf engine ('93-'96)
'CZ' is a 35 kW 1600cc Kombi engine ('79-'82)
'DZ' is a 84kW 1800cc Passat engine ('83-'84)
'EZ' is a 56 kW 1600cc Golf engine ('83-'87)
'FZ' is a 45 kW 1300cc Passat engine ('78-'83)
'GZ' is a 84 kW 1800cc Golf engine ('84-'88)
'HZ' is a 37 kW 1100cc Golf engine ('85-'91)
'NZ' is a 40 kW 1300cc Polo engine ('87-'92)
'WZ' is a 56 kW 1600cc Passat engine ('79-'80)
'Z' (by itself) is a 51 kW 1700cc VW 411 engine ('69-'73)
There is a 'ZB' engine but it's a 56 kW 1500cc Passat engine.