But the bliss didn't last long because Michaela and Zack proceeded to have their first fight, and Michaela's reaction was pretty explosive in which she was screaming and throwing things in the apartment.
During the September 1 episode of Married at First Sight: Unfiltered, Zack watched back a Season 13 clip of Michaela scolding him for allegedly disappearing on her one morning.
"You told me, 'I'm going to get [my dog] to bed and then after she's asleep, I'm going to come to the bed [with you].' That's the last thing I heard from you," Michaela tells Zack in the footage.
"The reason I didn't sleep in the bed with you is because I fell asleep. I was very tired. When I woke up, I had to take Bella to daycare," Zack explains.
"You never communicated that," Michaela snaps. "And I also don't see why you couldn't send a simple text message! You never came back!"
Zack argued that he had returned to their apartment around 9:15AM and Michaela was not home, which she called "bullsh-t."
"I was not gone at 9:15," Michaela insists. "You're a damn f-cking liar. You a g-damn m-therf-ck-ng liar."
Unfiltered host Jamie Otis -- who starred on Season 1 of Married at First Sight and is still married to her match, Doug Hehner -- noted how Zack and Michaela's reunion after his COVID-19 battle "went sour really fast."
"Did you lie?" Jamie asked Zack flat out.
"Absolutely not!" Zack replied. "The night before, I told her that I'm taking my dog to the daycare. She knew that. She knew it was going to be in the morning, but I did not tell her what time."
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Zack's fellow Married at First Sight grooms Gil Cuero and Johnny joined him on Unfiltered, and Gil offered his perspective on the big fight.
"Two wrongs don't make a right," Gil noted. "I feel like Zack was wrong. Even though [Michaela] knew, I feel like when you're married, there's more effort that needs to be done for stuff, especially when you don't know the person."
"I feel like you need to over-communicate. And then Michaela, that's just no," Gil said with a laugh.
"I don't have nothing to say about that -- she shouldn't have left! You can't. That's like kid stuff."
Zack acknowledged how he didn't understand Michaela's thought process in assuming he was never coming back to their shared apartment.
"All my stuff is there," Zack said with a laugh, before Gil agreed and said of Michaela, "That's extra! That's over the top!"
Zack confirmed he planned to return home to the apartment shortly after running his errand, but he gathered, "I could have sent another text message saying, 'Hey, sorry I fell asleep in the other bedroom.'"
"Something like that," Gil advised his pal, "just to kind of reassure her."
Jamie suggested Zack also could have left a note on the table.
"BRB! It's as easy as that, Zack! BRB. That's all it takes," Jamie joked.
Zack replied, "I learned my lesson. I learned my lesson."
When the pair met with Married at First Sight expert Pastor Calvin Roberson after the altercation, Zack said it hurt his feelings that Michaela didn't believe what he said and was so suspicious of him.
Michaela broke down into tears, saying she was nervous to let her guard down and totally trust Zack.
Michaela shared how Zack is a "phenomenal" man and she'd like to be with him for the rest of her life; however, she was worried about having safety and security since she had to protect herself after her beloved father's passing.
Michaela felt abandoned once her father died and struggled to let Zack take on that masculine role in her life and take care of her, and so Pastor Cal asked Michaela to allow Zack to be there for her and console her.
Pastor Cal also warned Zack that leaving the house stirred up something deep in his wife, who had to question where her new protector went. Zack couldn't relate to Michaela's traumatic experience, but he promised to have her back and be there for her going forward.
Michaela worried Zack was trying to take on too much responsibility, but Zack assured her that he wanted to do that and it wasn't too much for him.
"I don't want you to derail this early on," Pastor Cal told the couple as they appeared to get back on track.
Married at First Sight's thirteenth season, which currently airs on Wednesday nights at 8PM ET/PT on Lifetime, also stars Gil and his wife Myrla Feria, Johnny and Bao, Brett and Ryan and Rachel and Jose.