Scott finished third in this event back in 2003 but this is the first time he has played it since 2016 and the first time he has got out of the group stage at Austin Country Club since the format was introduced a year earlier.
The Australian birdied the second and never looked back on day three, winning the fourth with a par and birdieing the sixth to turn in 3 Up.
Another birdie came on the 12th and while Spieth hit back on the next, Scott never looked in trouble over 16 bogey-free holes.
"I played well today," he said. "I'm happy to get through that group. They're all tough groups but there were four Major Champions in this group and that kind of calibre player obviously knows how to get it done and has some toughness, so I'm glad to get through."
Justin Rose and Keegan Bradley finished All Square in the other match in Group 11.
Kisner won this event in 2019, one year after losing in the final, and he maintained his 100 per cent record in Group Six with a 4 & 3 win over Justin Thomas.
Marc Leishman was also a winner in Group Six, beating Luke List 3 & 2.
Hovland had claimed wins on days one and two and birdied the first in his match with Zalatoris to take an early lead.
The American won the second with a par and the duo exchanged birdies on the fourth and fifth before par was good enough to win Zalatoris the eighth.
A birdie on the 16th had Zalatoris 2 Up with two to play and while Hovland hit a beautiful tee-shot into the 17th, the last was halved in birdies and we went to extra holes.
The first was then also halved in birdies but Zalatoris took advantage of the fortuitous bounce on the second and a ten foot birdie saw him through.
The King of walking in putts 🚶♂️— WGC-Dell Technologies Match Play (@DellMatchPlay) March 25, 2022
Kevin Na is Round of 16 bound. pic.twitter.com/Iu2d7nIOYH
"It was kind of hard fought today against Viktor," said Zalatoris. "I basically played where I tried to make sure I just didn't make any mistakes. I made one mistake all day, really, and that's tough to beat but Viktor made me earn it today.
"New putter in the bag this week and a couple of little changes here and there on the off-week and nice to see it hold up under pressure really in the first week."
Kevin Na awaits Zalatoris in the last-16 after he defeated Maverick McNealy in a play-off.
Group 14 was wide open coming into day three and Na beat Joaquin Niemann 1 Up to finish alongside McNealy - who downed Russell Henley 2 & 1 at the top.
Na needed just one extra hole to beat his fellow American, holing a 13-footer for birdie to go through.
Cameron Tringale beat Sepp Straka 5 & 3 in the other Group Three match.