It looks very much like Trump and Z were having a fine conversation until Vance butted in. A lot of the things people are bringing up to complain about Z happened early, and Trump had no problem with them. In fact, even when Z and Vance started going at it, Trump seemed to listen to Z and look at Vance with an expression like, "That's a good point, JD, what do you say to that?" But then it kept going and something made Trump shift from Z to Vance and once he got on a rager there was no stopping it.
Either Vance and Trump teamed up on Z and ambushed him, or Vance waited or his opportunity to undermine Trump and sabotage the meeting. It certainly looks like the latter, which I hope isn't the case. But that's what it looks like.