England's Matt Fitzpatrick is in a share of the lead going into the final round of the US Open.
Fitzpatrick and Zalatoris are tied at four under after Fitzpatrick shot a two-under 68.
Defending champion Jon Rahm is a shot behind after he double bogeyed the 18th, with world number one Scottie Scheffler on two under.
The leader was just three strokes behind on one under.
Most of the movement was in the wrong direction as the USGA and Mother Nature combined to serve up a brutal test that even the best in the world couldn't deal with.
Seven players finished under par on a day when talent and bogeys were unavoidable. It was too much for him. The reigning Open champion signed for a 77 to fall out of contention.
Zalatoris and Fitzpatrick both played in the final group at the US PGA Championship, with Zalatoris losing in a play-off to Thomas.
They both have a chance to win their first major, but behind them are the defending champion, the Masters champion and a four-time major winner who are desperate for more.
The perfect storm of arriving at a familiar course, with his game in good shape and on the back of going close in the last major can tip the balance in his favor.
He had a closing bogey on 18 that prevented him from taking a solo lead, but he handled the course better than most.
In his short career, the 25-year-old has finished runner-up in two majors, including that USPGA Championship play-off loss last month.
Zalatoris only made one bogey as he avoided the mistakes that ruined the rounds of so many others.
Playing slightly ahead of the faltering leaders, Zalatoris was in the lead when he stood on the 18th tee and duly carved a drive miles right of the fairway, but rescued a par by getting up-and-down from a Bunker to show the Mental Toughness that Defined his Round
Zalatoris said that it felt like a 61 or 62 in his book. That's some of the best golf I've played.
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