I don't know about Zoom, but I run a video platform and you can definitely have 1000 people on a call. The caveat is that you can't consume everyone's video and

I don't know about Zoom, but I run a video platform and you can definitely have 1000 people on a call. The caveat is that you can't consume everyone's video and audio, so consuming a new person's audio and video takes a second or two. This works fine if you have 2-20 main speakers and a few of the 1000 people "raising their hand" to talk.