On a brutal day of Saturday scoring in windy, firm conditions, Zalatoris, 25, posted a brilliant 67 to move to 4-under par.
England's Fitzpatrick, 27, had moved one shot ahead after a birdie at 17 but he handed it back on 18 to card a very solid round of 68.
Zalatoris and Fitzpatrick have both been playing some exceptional golf on the PGA Tour of late but neither has yet tasted victory on the circuit.
They will both be looking to set that record straight on Sunday.
Zalatoris lost out in a playoff to Justin Thomas at the US PGA Championship last month, while Fitzpatrick has notched three top-10 finishes in his last four starts.
But it's far from a two-horse race at the US Open, especially with a number of star names hot on their heels.
Defending champion Jon Rahm is just one shot back on 3-under par, while World No.1 Scottie Scheffler is two back alongside Adam Hadwin and Keegan Bradley.
Scheffler had moved to 6-under par earlier in the round but the wheels quickly came off him thereafter with a double-bogey at 11 followed by bogeys at 12, 13 and 14.
The reigning Masters champion did recover a shot back on 17 though and he remains in contention for a fifth title of the season.
Rory McIlroy struggled for much of the day but he is still in the hunt for a first major in eight years at 1-under par alongside an in-form Sam Burns.
Keep up to date with all the latest updates and scores with our LIVE commentary of Round 3 of the US Open...
Quite the day.
A fun watch from start to finish.
The leader board chopped and changed all afternoon.
But it's Will Zalatoris and Matthew Fitzpatrick out in front.
Keegan Bradley, Adam Hadwin, Scottie Scheffler, Sam Burns, Rory McIlroy and Joel Dahmen are right there.
And don't rule out the others lurking below.
It's the US Open, afterall...
Thanks for following the coverage on GolfMagic today.
We'll see you tomorrow.
Rory McIlroy says he's still right in the tournament.
It was a tough day for the Northern Irishman and he just had to grind out the pars on the back nine.
He tells Sky Sports he just wants to get his hands on a major again.
Elsewhere, Collin Morikawa has just put the finishing touches on a 77 and he falls six shots back of the lead.
His playing partner Joel Dahmen just misses out a birdie putt on 18 but he, too, is still right there at 1-under for the championship.
Jon Rahm's mistake looks to have cost him dearly here.
He smashes the ball out of that fried egg in the sand and marches up to his golf ball on the green.
There's a few chirps from the crowd and he complains: "Give me a break, guys!"
His putt from about 25 feet doesn't break to the right and it will give him a finishing double bogey.
Sick.
He drops back to 3-under and now it's Will Zalatoris and Matthew Fitzpatrick who will be in the final group...
My word.
Jon Rahm finds the fairway bunker at 18.
He's only got 137 yards into the pin but he's smashed his approach into the lip and he's still in the bunker.
Good grief.
He plays his third into the front bunker protecting the green and he's plugged...
Can he make a five?
McIlroy got lucky at 18 with his tee shot.
He was left with a wedge in but he had to hook it round a tree.
He did so brilliantly and got a huge, huge roar from the Boston crowd.
His birdie putt is so very close but a par will have to do.
It's a 73 for McIlroy. He's not out of it at all.
What an interesting day for McIlroy...
Jon Rahm takes the lead with a birdie on 17.
He played that hole brilliantly. Lovely drive and his approach ended up inside 10 feet. Of course he drained it.
And yet again there is more trouble for McIlroy on 18.
His drive is shocking. It's so far left.
Will his putter save him once again?
In case you missed it, Bryson DeChambeau carded a 6-over par 76 and sits in T-55 after 54 holes at 8-over par for the championship.
It was also a forgettable day for Brooks Koepka and Xander Schauffele.
Koepka fired a 5-over par 75 and Schauffele was one stroke better.
The 36-hole leader, England's Callum Tarren, has carded a 78. He's at 7-over now and in a tie for 49th.
Yep.
Terrible tee shot on the drivable par-4. Then he thins his short wedge into the rough and leaves his chip short.
Does it matter?
Of course not.
He drains another one.
Just tremendous resolve from the Northern Irishman.
Meanwhile, a huge par putt drops for Scheffler at 18 to card a 1-over par 71.
What a back nine for Scheffler.
Jon Rahm is now at 4-under par and he was so close to moving into the outright lead at 16.
His downhill birdie putt from around 21 feet stops about an inch short.
Meanwhile more trouble for McIlroy, who is fighting to save another par at 17...
Rory finds the bunker at the par-3 16th.
Of course, he hits a beautiful shot out of it and adds another gutsy par to his collection at The Country Club this week.
Birdie at 17 for Scheffler.
He's two back. But man, what a back nine for the 25-year-old
Fitzpatrick can't get up and down at 18 and he closes with a bogey.
He's at 4-under, tied with Zalatoris.
His playing partner Sam Burns is at 1-under going into Sunday.
Meanwhile, can someone check on Rory McIlroy?
He's just saved another par.
I've lost count of how many times I've written that this week.
Rory has poured gallons of “not dead” into the stew.
— ANTIFAldo (@ANTIFAldo) June 18, 2022
Slap a ‘Whoosh’ on this and give it to Rory to wear when he collects the trophy tomorrow night. pic.twitter.com/NTlx6FDl4g
— Michael McEwan (@MMcEwanGolf) June 18, 2022
Fitzpatrick -5
Zalatoris -4
Rahm -3
Bradley, Hadwin -2
McIlroy -1
Scheffler -1
Burns -1
Dahmen -1
Rory makes do with par at 14 when birdie was in the equation after his tee shot.
Fitzpatrick is in trouble at 18. His tee shot was miles right and his approach stalls against the wind and lands in the front bunker.
Tough up and down from there.
Still, whatever happens he's gonna have another chance.
Just like he did at Southern Hills.
Scottie Scheffler's birdie putt on 15 teaters on the edge of the cup.
It doesn't drop.
And he looks fed up.
Like, really fed up.
Elsewhere, McIlroy's second into the par-5 on 14 clips a branch and his tricky pitch from the rough leaves him with a tough putt up the hill to make a birdie.
Meanwhile, Matthew Fitzpatrick has just taken the outright lead with a birdie on 17.
He's at 5-under!
It's no tea party at this US Open, says Sky Sports' Nick Dougherty.
And I'm inclined to agree.
Golf fans are just loving the brutality of it all:
Me with a 1-shot lead on 18. #usopenpic.twitter.com/JMrwvga3Jx
— robmillertime (@robmillertime) June 18, 2022
Jon Rahm makes bogey at 13 to drop back to 2-under.
Poor putts then cost Collin Morikawa, who now is 4-over par for the tournament and 1-under for the championship.
Morikawa will need a strong finish to keep himself in the mix.
Can we just pause for a moment to say that less than two hours ago the Masters champion led this US Open by two shots.
That was after he holed out for eagle on his front nine.
Now he's three strokes behind.
From the 10th hole, he's made a double bogey and three consecutive bogeys.
Just as I type this, Jon Rahm is not a happy bunny.
"What a FREAKIN day!" he yells after the wind catches his approach into 13.
Huge, huge, huge putt there for McIlroy at 13 to save par.
He was in ALL SORTS of trouble.
But he drains the putt and will head to the 14th still at 1-under.
It's a par-5...
Matt Fitzpatrick for the co-lead!
Back-to-back birdies tie him with Will Zalatoris atop the leaderboard on Moving Day at the #USOpen.
: @nbc and @peacockTVpic.twitter.com/tDTCA0vEPX
— Golf Channel (@GolfChannel) June 18, 2022
HERE COMES THE ENGLISHMAN!
Birdie-birdie for Fitzy.
He's at 4-under!
He's thru 15 holes.
Jon Rahm is 3-under par after 12 holes.
He's stalked all of his putts today from every angle.
These greens are quick and it's just super hard to make a par.
That's another hole ticked off for the former World No.1.
Meanwhile, McIlroy has an outside chance for par after having to chip out after another wayward tee shot.
2014 PGA Championship winner Keegan Bradley will be in the conversation tomorrow.
He's at 2-under par for the championship after carding a 1-under 69.
This is how he finished:
Hometown hero @Keegan_Bradley in the @usopengolf mix. pic.twitter.com/XyvjnDacpT
— Golf Central (@GolfCentral) June 18, 2022
I don't think anyone is really enjoying it out there at the moment.
It's a hang-in-there sorta day.
Collin Morikawa (-2) and Joel Dahmen (-1) both make par at the 11th.
Meanwhile Will Zalatoris, the current leader by one stroke, says his 3-under 67 felt like a "62".
Tomorrow he'll contend in the final round of a major once again after near misses at The Masters and the US PGA.
And as I type this, McIlroy is in trouble again....
