Auckland's Emma McCosh cruised home comfortably in third, posting 3h 20m 41s, while McKenzie - though she couldn't maintain her valiant early charge - was still good enough to hold onto fourth in 3h 26m 47s.
The men's race was far closer, with Australian Jarad Kohlar needing a last-kilometre kick to get in front of Nelson's Trevor Voyce.
Kohlar had a memorable day, falling out of his kayak near the end of the first leg and losing a drink bottle on the mountain bike but he held his composure and had enough to withstand Voyce's challenge.
"I was running a bit dry at the end but sat on Trevor's heels for the last lap and put the pressure on up the final little hill," Kohlar, who was third in the 2011 race, said. The 31-year-old crossed in 2h 46m 08s, with Voyce finishing just 27secs back.
"I had a good ride with Jarad and felt pretty consistent on the run," Voyce said. "I didn't do anything special and it was my strongest performance at 3D, although I'm definitely gutted I couldn't get Jarad near the end."
Whakatane's Sam Clark made all the early pace with a slick kayak and a solid mountain bike but a niggling groin injury returned to haunt him on the run. He eventually finished fifth.