Its not described as a zg. Just a 240z (G-nose).
It also says this if you want to, believe that too :
The 240Z's looks were spot on, thanks to styling influenced by a Count Albrecht Goertz concept developed for Datsun in the early 1960s. Performance from its sporty 2.4 litre power unit which owed a lot to the BMC C-Series as well as Mercedes-Benz's straight-six, was more than ample. Being a Datsun, reliability was a given, but the agile (if tail-happy) handling was a pleasant surprise.