If you don't mind overnighting in SIN on the outbound you can do YVR-SIN-SYD-AKL-SIN-YVR. YVR-SIN-SYD/AKL-SIN-YVR on SQ and SYD-AKL on NZ. As for NZ Y, their seat pitch in is 34" for 744 and 32" for 777. You'll get descent meals and IFE in definite with SQ even in Y. For certain booking classes, you do get status mileages for both
SQ and
NZ.