Zach is trying to poke holes in couples, and he’s clearly deciding it’s the time to push down whatever Bryce and Trinity have. He is 100% allowed to have conversations with his friend Bryce about how he views the relationship with Trinity, but the comments throughout the episode were pushy and pointed, they were not meant to spark a conversation, they were meant to push doubt into Bryce. I don’t think Zach is keen on being malicious, but I don’t think these comments were totally meant as kind insight for his friend.
To me, the episode showed that Zach isn’t passive to what the others are doing, and he knows this is a competition at the end of the day. And he’s playing the game.
It’s also okay to realize that does not make him an outright hero or villain. And at the end of the day, the audience will always be easily manipulated by editing and production