Create a live video feed

Hi, This is a software job. I'm looking to create a project that takes video (pre-recorded) and calls them into a live video feed. I want to be able to have a number of videos on the feed side by side, imagine splitting the screen into a grid, and having each section of the grid as a separate video. A scenario below: Imagine you are on a zoom call, and you want to pretend that you and your colleagues are in the call. You want your webcam to show a split screen view of your colleagues, showing maybe 6 or 9 at a time. You want to be able to control which of your colleagues are being shown on the screen, and have pre-recorded video of maybe 10 colleagues. You chose which of your 10 colleagues are shown on the screen, and this is then replicated in the live video. Ideally, the video feed should them be selectable as a webcam, however this is not project critical, as systems like “manycam” exist that can do this – if possible, then great. To summarise: -take multiple video’s -have them be called into a feed, showing maybe 9 videos at any one time, side by side. I should be able to select whcih 9 videos i want shown in the feed in REAL TIME -have the live video feed broadcast as a webcam (not critical) It's a software project, that handles video. Im essentially wanting a qoftware that can display a number (9) videos onto the screen as a grid, and have the ability to select which videos are shown in real time. The key is selecting the video in real time, as anyone can create a montage of 9 video clips!" Thanks