Relatively easy as long as

Relatively easy as long as your camera is locked down on a tripod. If the camera moves, you’re wasted. Just shoot the scene 4 times – one for each character – all without ever moving the camera.

Stack all four videos on top of each other in your editing timeline (four video tracks/layers). Crop the left and right of each one appropriately and you’re good to go.

What are you editing with?