Looks like it started with JD saying that Zelensky wasn't "thankful" and was instead trying to plead (JD said "litigate" IIRC) his case to the American public (which of course he was, that's what these meetings are for otherwise you have them in a private room).
It was already under tension because it looked like they couldn't come to terms. When Zelenskyy accuses Trump of being aligned with Putin, things started getting heated.
> When Zelenskyy accuses Trump of being aligned with Putin
When was that, I haven't seen the whole thing except where it got heated, but at no point did I catch Zelenskyy saying anything that could possibly be interpreted like that.
But mostly I couldn't hear what Zelenskyy was saying because he couldn't get a word in edgewise.