Currently, Vizard might perceive both the speaker and screen share as one screen if the speaker window is stacked on top of the shared screen. To manually edit the speaker, click on the image, then select the edge of the frame to edit until it leaves one speaker, then right-click on "scene"(the timeline)--"Duplicate original video", and click the image again to cut out the shared screen.
We recommend recording the Zoom meeting using a non-overlaid, side-by-side mode before editing. Check out this detailed tutorial from Zoom.