The Oracle team returned to the water after a five-day break, showing greater speed, but struggling with stability and manoeuvrability.
The Kiwis won their fifth straight race to take a 4-0 lead in the first-to-seven format, first up today.
Oracle skipper Jimmy Spithill made a big tactical mistake at the start, gaining the best position on the line, but encroaching early for a two-boat length penalty.
Emirates Team NZ led by a few seconds around the first two marks, but helmsman Peter Burling had to withstand Spithill's aggression and a faster Oracle ACC boat upwind in 11-knot breezes.
The American team actually took the lead briefly up the third beat, but copped another two-length penalty for crossing too close to the NZ boat. That proved the decisive moment of the race and soon afterwards, Oracle fell off their foils in a gybe, to concede several hundred metres.
The final margin was more than two minutes.
"We just approached this like any other race," said Burling afterwards. "It was nice to have five days off, and give the shore crew a good opportunity to work on the boat and make this great boat we've got a little bit quicker.
"We also managed to get out for three training sessions as well, to sharpen up all those little things, those little scenarios. That really showed today in the pre-start - we probably didn't milk that penalty as much as we should have.
"But to have full confidence in our strategy and our plan up that second beat, and force the issue, force the penalty and win the race was really pleasing for us.
"We've been expecting these races to be a bit tighter like that, but we feel we've got really good boat-opn-boat stuff now to be able to deal with it."
The changes to the Oracle boat over the past week seem to have made it faster upwind, where the Kiwis held a big advantage last weekend, but the defenders may have sacrificed manoeuvrability and crewwork still wasn't nearly good enough to make up the margin between the two teams.