I am under the impression that you are trying to split the front half from the back half? In hopes of just running the front half or "engine bay side" of the A/C delete box with your existing system, essentially you just trying to change the cover? Because if you are, that will not interchange, you need a complete system(duct work, controls, cables, everything), they don't have the same back sides, nor are they interchangeable in that way.
But if you simply just wanted to take it apart, there are screws on the back side, and you then must remove one of the arms(press fit onto) on the end of a door flap rod to actually separate the front from the rear.