It's not possible directly from the routine. But if you have a spare Echo Dot you can have another routine that instructs the Echo Dot to say "Alexa, show backdoor camera." You would put the Echo Dot close enough to the Echo Show so that the Echo Show will hear the command and display the video from the camera. It's kind of redundant, but that's the way it works for now.
The only device that I know of that works directly to show the camera video when motion is detected is the Ring Doorbell. And that's probably because Amazon owns Ring. And it seems Amazon supports Ring products better than any other manufacturers. If you browse the forums you'll see that many people have difficulty integrating Alexa with motion sensors from other manufacturers. But there are no problems with Ring Alarm motion sensors.