Swith bettwen 2 DirectX applications

Hi! I wonder, is there some possibilities to make what I want:

1. I have renpy library, that is python written visual novel engine.
2. And I have Unity3D, C#, DirectX 10, which can load plugins.

I want to switch between those applications dynamically in realtime, at some point player will leave renpy engine, play inside Unity, then get back.

What is the best way to get it done? Maybe, using some 3rd application to wrap around those 2 - any points or directions you can give me on this to research?
Or maybe I can intercept renpy DirectX rendering, and redirect its final image output(screen) into Unity?

Thanks!