The current record holder was 18 years and 41 days old when he finished. When Zac hits the water, he'll be just over 16 years old.
"I have a little less than two years, and I should be able to do it in a year and a half, probably a little less," said Zac.
Time may be on his side, but there's a lot of water out there that's betting against him.
"The ocean is very unforgiving and not very friendly," said Laurence Sunderland, Zac's father.
Zac's dad Laurence is a lifelong sailor. He knows about the dangerous weather and pirates who roam international waters. But he says Zac is both determined and prepared.
"He's more than qualified," said Laurence. "The ocean has been his playground and he treats it with the necessary respect that I feel comfortable allowing him to do this trip."
"I've lived on boats my whole life, about nine years on boats," said Zac. "I've cruised Mexico and the Channel Islands for three years with my family, got about 15,000 miles under my belt."
At 36 feet, the Intrepid is a good-sized yacht, but not big enough to bring all the comforts of home. Zac will definitely be roughing it. But one thing he won't be able to leave behind is homework.
That's because along with the state-of-the-art weather-tracking gear, Zac's boat will also have a satellite phone and Internet link that can easily transmit schoolwork.
"I've tested out of high school on most of my subjects, actually, so I'm gonna continue doing it, and continue my education on the boat and send my tests back and do my stuff over the Internet," said Zac.
But Zac's mom Marianne admits homework won't be the priority here, that Zac will have other things to worry about.
"I know that he will have times where he's having hard times and no mother wants to know that their son is going to go through that," said Marianne. "But he knows that it's not important how old he is when he gets back, it's important that he get back."
Back being the ultimate destination, hopefully via the record books. And though Zac may be sailing solo, he knows his family's definitely onboard.