One stroke off the lead overnight after opening with a six-under-par 67, the American broke clear of a log-jammed leaderboard as he fired a seven-birdie 66 in the elite, winners-only US PGA Tour event at the picturesque Kapalua Resort.
Though Johnson did not birdie any of the four par-fives on the hilly Plantation Course, he hit a series of wedge shots close to the pin on the par-fours and putted well as he posted a 13-under total of 133.
Matt Kuchar (68), Jordan Spieth (70) and champion Dustin Johnson (66) were tied for second place, with fellow Americans Webb Simpson (71) and Michael Thompson (71) a further stroke back at nine under.
Zach Johnson, who upstaged tournament host Tiger Woods in a play-off to win the Northwestern Mutual World Challenge in California last month, was delighted to see the prevailing trade winds return to Kapalua on Saturday.
"If you have the proper winds, for me not being a bomber, I feel like I can take advantage," Johnson, who is known for his accuracy off the tee and brilliant short game, told Golf Channel.
"There were a lot of wedges today and that's where I've got to continue to stick it close, with those wedges."
Johnson's sole regret on another mainly sunny day on the Hawaiian island of Maui was his mediocre performance on the par-fives.
"You know I parred every one of them," said the 37-year-old, a 10-times winner on the US Tour. "I had a three-putt on one of them for par, which can happen.
"A couple of missed opportunities, certainly one at the last, and also at 15, but I putted well today."
Long-hitting Dustin Johnson, who triumphed by three shots last year in a tournament reduced to three rounds and forced to a rare Tuesday finish because of relentless howling winds, birdied all the par-fives as he surged into contention.
"This golf course sets up well for me," said the 29-year-old American, who clinched his eighth US Tour title at the WGC-HSBC Champions in Shanghai two months ago.
"I can reach all the par-fives and then there are a few short holes where you can drive it up close to the green. If I chip and putt it well, I'm going to shoot a good score pretty much every time around here.
"It was back to a pretty normal wind here today ... I thought the golf course played a little tougher yesterday. Today it was in great shape and I played a little better," said Johnson, who birdied six of the first nine holes.
Masters champion Adam Scott of Australia, the world number two and highest-ranked player in the elite field of 30, carded a second successive 70 to end the day at six under, seven strokes off the pace.
- Sports & Recreation
- Dustin Johnson
- Jordan Spieth
- Matt Kuchar