Tayshia, 30, selected Zac, a 36-year-old addiction specialist from Haddonfield, NJ, over Ben Smith in her final days of filming The Bachelorette's sixteenth season, and she and Zac got engaged at the Final Rose Ceremony that aired on December 22.
Zac joined Tayshia and her co-hosts Joe Amabile and Natasha Parker on this week's episode of their Click Bait podcast and discussed he finally felt like Tayshia was truly into him and their relationship during a champagne toast one evening.
"There was no drinking on the show," Zac, who has recovered from previous drug addictions and alcohol abuse, shared on the podcast. "Sober to me means no drugs, no alcohol, no nothing -- since August 2011."
Zac shared how he only drank sparkling apple cider or even ginger ale for those toasts.
"Who's going to claim they're sober and then when it comes to a toast, say, 'Oh, just one glass of champagne!' You know what I mean?" Tayshia said.
"Can I tell the story though?" Zac sweetly asked his fiancee, clearly excited to share it.
POLL: DO YOU THINK TAYSHIA AND ZAC WILL END UP GETTING MARRIED?
"Please!" Tayshia exclaimed.
"We've been asked a lot the moment that I knew Tayshia liked me," Zac said, before looking at Tayshia and asking, "You know this, right?"
"Mhmm," Tayshia replied.
"So after the Rose Ceremony, there is always this round of toasts. So we were getting down to maybe, like, five guys. And the guy came out with the tray of champagne and there were four champagnes and one apple cider," Zac recalled.
"And [Tayshia] looked at me and she goes, 'No, I'm drinking apple cider with him tonight.' And I was like, 'What?!'"
Zac elaborated, "So she made the guy go back and get apple cider while all of us were waiting. So she was on 'Team Clarky' that day. And that's when I knew! I was like, 'Okay!'"
"You've got her!" Joe interjected.
Zac concluded, "It's a personal choice. So if someone is in this dark, deep hole and they're hammering drugs and they come out of that and they're able to drink here or there, props to them. But for me, my choice and my best life is no nothing. And that's something I'm committed to."
In a 2014 speech, Zac reportedly said his addiction resulted in "15 years of lying" and culminated with a four-and-a-half month stint at a addiction recovery facility that helped him turn his life around.
According to a report the Reading Eagle published at the time, Zac spoke at a gathering at Alvernia University in January 2014 and detailed the lengths of his addiction.
Zac apparently once complained of a pain in his side and asked doctors to remove his gall bladder so he could have access to heavy painkillers. He was also thrilled to receive drugs after a brain tumor was removed from his head.
The report says Zac snorted and smoked OxyContin, shot heroin intravenously, smoked crack and did "whippets," which is inhaling bursts of nitrous oxide for a short-lived high.
"She has a one-way ticket to New York," Zac told the magazine of the California girl. "We're going to get comfortable. And I'm going to date the heck out of her!"
"I'll still have my place in California so we'll be bicoastal, but that's the plan!" Tayshia added.
The couple admitted they're "not rushing" into a wedding and marriage, but Tayshia told the magazine, "It's an amazing sense of security to know that I'm not going anywhere, and he's not going anywhere."