Chasing a moderate target of 244, the Kiwis were all out for 157 in the 44th over with Mitchell Starc taking tournament-best figures of 5-26, his second 5-for of the event.
Australia, still the only team to have qualified for the semifinals, is heading to the playoffs showing ruthless improvement in every appearance.
Earlier, pace spearhead Trent Boult hogged the limelight with a sensational last-over hat-trick to stop Australia's rebuilding job at 243 for nine in their ICC World Cup match.
With his swinging full-pitched deliveries, Boult sent back the well-settled Usman Khawaja (88 off 129 balls), Micthell Starc and Jason Behrendorff, while giving away just two runs at the Lord's.
For Australia, Usman Khawaja made 88 and Alex Carey 71 in a fightback worth 107 for the sixth wicket after top-order failure.