"That tied my best round here (Omanu) and kept up my good form. I enjoy Omanu a lot more because it is more open so I can hit a lot better tee shots because there are no trees," he said.
The victory followed his triumph in a top-class field at the North Island Men's Under-19 Championship played at St Andrews in Hamilton a week earlier.
Hillier won by defeating his older brother Charlie, 19, by one shot in a final-hole finish the two sibling rivals will never forget.
He needed to get up and down from a bunker at the 18th for par to beat his older brother, who was watching greenside, by one shot.
"My ball was plugged. They have hard faces on the bunkers so I had an idea of just bouncing it into the bank and letting it run down the slope and pulled it off perfectly. It ran down to about nine feet and then I holed it across the slope for probably the best moment of my life," Hillier said.
"Our competitiveness is unbelievable so it was actually good to get one over him [Charlie]. He came up to me and said 'good golfing brother, you finally got one over me', which was nice."
The win was even more remarkable as Hillier broke his toe the night before the final round and struggled to walk round the course.
"That was the best thing about the week - breaking my toe and still winning."
Charlie won the event in 2014 and was home for a month after an outstanding first year at University of Kansas, where he is number two on the famed golf school's Jayhawks team.
The younger Hillier would like to lead the Bay of Plenty senior golf team at the Interprovincials later this year and then play college golf in the US, before launching a professional career.
He said they had come through a positive, nurturing environment at the Te Puke Golf Club which has been a big factor in his success so far.
"I can't thank those guys enough. They support me financially and I owe them so much."
