Zanna grabbed the first of his 21 rebounds – the most ever against a Roy Williams-coached UNC squad – on UNC's opening possession and established his presence from the outset.
Pittsburgh scored seven points off Zanna's three first-half rebounds and posted a 9-2 edge in second-chance points in taking a 36-26 lead at halftime.
James Michael McAdoo attributed Zanna's success to his activity level on the glass.
"Getting to the boards and having effort," McAdoo told reporters following UNC's 80-75 loss. "I think part of that is on us, just not doing a good job checking off each and every time they got a shot up. I think he did a good job of going to the front of the rim. A lot of the balls just dropped right in front of his hands."
The Tar Heels had no answer for Zanna after halftime as the fifth-year senior grabbed five offensive rebounds in the opening seven minutes. He grabbed offensive rebounds on four consecutive possessions and capitalized on three with tip-ins.
"We went smaller and that allowed us to penetrate and it made them rotate and allowed him to get some offensive rebounding position," Dixon said. "But, obviously, he has a knack for it. He's always been good at it. He's on the glass constantly. He used his quickness. They had some bigger guys guarding him and that was to his benefit."
Zanna, who was averaging 10.5 rebounds over his previous eight games, finished with 21 rebounds. Pittsburgh scored 19 points off Zanna's 10 offensive rebounds.
"You can't beat a good team if one person by himself has 10 offensive rebounds and scores most of them," guard Marcus Paige said.
Pittsburgh's 43-35 rebounding margin marks the third time in four games that UNC has lost the battle on the boards. It's also the 12th time in 17 games that the Tar Heels have allowed their opponent to grab double-digit offensive rebounds.
Duke outscored UNC, 20-10, in second-chance points on Saturday on a 16-6 offensive rebound differential.
Both teams entered Friday's game ranked in the top-20 nationally in offensive rebounding percentage.
"They got too many offensive rebounds on us," forward Brice Johnson said. "They beat us on the boards. That's the one thing we've been preaching the entire year. We want to be better on the boards than our opponents are. They beat us on the backboards and that was the difference."
McAdoo and J.P. Tokoto led UNC with seven rebounds, while Johnson added six.
One glaring omission for most of the game on UNC's interior was Kennedy Meeks. After being limited by a stomach bug in the loss at Duke, the freshman center played just eight minutes despite starting both halves.
When asked if the virus was having lingering effects, Williams quickly said no before launching into a critique of his 5-spot.
"The coach has got to put in the guys that he thinks is going to do the job at that specific time," Williams said during his postgame press conference. "I didn't think we were getting as much out of Kennedy as we could have gotten. I had Brice in there, I had Joel [James] in there and had Desmond [Hubert] in there.
"Brice did some really good things. He's got to get better defensively. Same thing with Kennedy. Kennedy has had some unbelievable good games for us. At the same time, he's had some games where he hasn't played as well. The games that he's not playing as well, I've got to get some other guys in there that will play better."
Zanna's dominance on the boards not only secured UNC's early exit from the ACC Tournament, but it also highlighted the fragile state of a frontcourt that appeared to stabilizing just several weeks ago.