When we run Wirecast audio and PGM video into Zoom as a virtual sources, we get 1s of a loopback (echo) of all audio and people's voices in Zoom when cutting back and forth between a screen capture with Zoom as a shot, and a media file (video playback). The problem corrects itself after 1 second without us changing any settings. Our audio is routed properly with the help of Loopback audio software. I think this is just a stupid wirecast to zoom bug.
When you export a Set, you will be prompted to choose a name and location to save your file. The file name will end with .wirecastkeyset. You can then move this file to another computer and import it to another Wirecast document using Configure >Import.