I’ve got a multicam sequence and I spent a lot of time on it cutting out lots of material. Now I decided to show two cams simultaneously for a while. But how to do this? Can anybody help?
You don't say what video editing software you are using, but assuming it's either Adobe's Premiere Pro, Davinci Resolve, or FinalCut Pro X, the general answer is the same. Multicam is a convenience for you as an editor to use a special viewer in your NLE to view (and cut) multiple camera angles at the same time. To output two cameras simultaneously, you need to have two video layers visible at the same time, one for each angle. If you zoom and pan one video layer so that it occupies the left side of your output and you zoom and pan the other video layer so that it occupies the right side of your output, you can show two cameras at the same time.
Another way to show two video camera views at the same time is picture-in-picture. In this case, one layer can be full-sized and a second layer, placed on top, can be zoomed and panned to wherever you want the picture-in-picture image to be (usually lower right).
It doesn't really matter whether the video layer source is an active mulicam or a flattened multicam (which resolves to a simple video layer). What matters a lot is that you have scaled and located the video footage so that both layers are visible at the same time.