During the April 1 broadcast of Married at First Sight: Unfiltered, Zach watched back a Season 10 clip of Mindy confiding in her friends about how Zach had heard from somebody Mindy was planning to see her ex-boyfriend.
Mindy's best friend Shannie suggested it was probably Lindsay who had spilled the beans because she had mentioned to Lindsay how Mindy's ex wanted to pick Mindy up from the airport following her Panama honeymoon.
At this point, Mindy was already aware Zach and Lindsay had been building a friendship behind her back, and Mindy naturally felt betrayed.
Unfiltered host Jamie Otis asked Viviana, "Do you believe Zach is being completely honest with Mindy about his relationship with Lindsay?"
"No, I don't!" Viviana admitted. "Because I think [Zach] may not even realize what the relationship was really all about."
"Right," Zach agreed.
"So, for sure, I don't think you'd be able to then relay that information to your wife," Viviana elaborated.
"There's a difference between privacy and secrecy, and when you have to keep a secret -- and it's not going to end with, 'Surprise, I booked you a trip!' -- it's probably a good sign that it's not a good thing."
After "connecting the dots," Zach apparently realized he had made a big mistake in his marriage.
It was clear Zach and Lindsay both wanted to hide their conversations, and they also told Mindy different stories when it came to how often they communicated and what their conversations were truly about.
Zach, for instance, insisted he just wanted advice on how to deal with Mindy and proceed in his marriage, but Lindsay claimed she and Zach were building a friendship outside of Mindy being the topic.
Jamie therefore asked Zach what Lindsay might have been trying to hide from Mindy.
"She talked about how, oh boy, how Shannie would walk Mindy to a ledge when it came to tough-conflict type of conversations and in the midst of that would be like, 'But Mindy's great, give her a chance,' and there was, like, a lot of back and forth," Zach admitted.
"But she was trying to come across as transparent from the bigger picture standpoint by talking about her friends."
Viviana, however, did not think Lindsay had Mindy's best interests at heart.
"I think she just wanted to get your attention and keep it," Viviana confessed.
"Yeah," Jamie agreed.
"I mean, Mindy is a good communicator," Viviana insisted, before telling Zach, "If you had questions about Mindy, she would probably have told you the good, the bad, and the ugly."
And Jamie backed Viviana on that and said, "Yeah, she's not too scared to admit any of it."
Shortly after their wedding day, Zach admitted to Mindy on several occasions he wasn't attracted to her and they lacked intangible chemistry.
Zach claimed on the April 1 broadcast of Unfiltered that Mindy was fragile in their relationship and lacked self-esteem, so he suggested the Married at First Sight experts didn't do a great job of matching them to begin with.
Despite her bruised ego, Mindy forged on with optimism and hope, but Zach hindered the possibility of forming an intimate connection by keeping his distance from his wife and refusing to move into an apartment with her.
Zach's secret relationship with Lindsay and lies he told Mindy in order to protect Lindsay resulted in Mindy ending her marriage nearly two weeks before "Decision Day."
"What I've learned is no matter how much I wanted it, a marriage is not about one person and my husband did not show up to be any kind of decent partner," Mindy griped in last week's episode.