Zach felt like something was "off" with Kat for a couple of weeks. When Kat attempted to explain to Zach that she temporarily had doubts but truly cared for him and saw a future with him, Zach still denied her a rose and chose not to give their relationship another chance.
This isn't the first time Nick has criticized Zach's behavior on social media.
"That's 2 weeks in [a] row now Zach was a total d-k to one of the [women]. It's literally all about the one on one. Zach knows that," Nick tweeted last month. "He made Jess feel like she messed up for expressing a valid concern. #thebachelor."
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Nick also wrote, "Zach is acting like the guy who gets mad at his girlfriend for not letting him know she wanted validation on her birthday."
During the February 27 episode of The Bachelor, Jess expressed to Zach how she was disappointed, frustrated and losing confidence in her herself and their relationship because Zach had yet to invite her on a one-on-one date.
Other than Greer Blitzer -- who was diagnosed with coronavirus after visiting London and had to quarantine -- Jess was the only woman who had yet to accompany Zach on a solo date by the time they traveled to Estonia, which was Week 6 of Zach's journey to find love.
Instead of comforting Jess and validating her concerns, Zach essentially scolded the bachelorette for being focused on the wrong thing, which led to a tense exchange.
Zach seemed bothered and surprised by Jess' emotion over her string of group dates, which she insisted to Zach was "a big deal" to her and every other woman on the show.
"That shouldn't be a thing," Zach snapped, later adding, "I never want you to think of this as a process, where you can only open up on a one-on-one."
Zach ultimately pointed out how he and Jess had "a disconnect," and so they seemingly mutually agreed to part ways.
Jess told Zach that she wasn't going to fight for him because she deserved and needed a man -- after painful failed relationships in her past -- to fight for her, and Zach told the cameras that he and Jess were "butting heads" and he never expected their romance would end that way.
For Jess' part, she left the show in tears and a bit angry, venting in a confessional, "This doesn't feel fair... I have done everything that he has asked, and... all I needed was quality time, and he wasn't processing that."
Jess continued, "Is it the craziest thing to want to go on a date with somebody I could potentially marry? Like, it's the craziest thing that I'm upset that I'm the last one [without a solo date]?"
"I think he's an amazing guy. I think he was doing the best he could in the moment," Jess said.
"I was doing the best that I could in the moment. We both just weren't understanding each other, and it doesn't mean that I was in the right and he was in the wrong."
Jess insisted there was actually "no right or wrong," especially since Zach was just "speaking his truth."
"I was speaking mine the best that we could, so I was not ever upset with him. It was more of just, like, I wish we could have understood each other," she concluded.
Many viewers also thought Zach was rude to Greer while he was quarantining in London.
Zach had snapped at the Houston-based medical sales representative via videochat for comparing his battle with COVID-19 amid his The Bachelor journey and pursuit of finding a wife to her prior positive COVID-19 test during a busy time at work.
Zach claimed their situations were "completely different."
He told Greer, "I just had to put it out there, like, it's not the same. In a few short weeks, I could be standing in front of my person, and that means a lot more to me than the end of a sales quarter."
Greer took to Instagram after the episode aired and appeared to throw shade at Zach by writing on February 21, "Women who care about their careers are hot."
While Nick -- who appeared on multiple seasons of The Bachelor franchise but is currently happily engaged to someone outside of Bachelor Nation, Natalie Joy -- has scrutinized Zach for his actions on the show, The Bachelor alum Susie Evans is all about it.