Clear depth buffer between two layers

I am trying to draw a layer, clear the z-buffer and then draw the other layers. But I don't seem to have the access in Unity to call the camera's functions in between drawing.

I want to do this, because I want to draw the sky and then clear my depth buffer again, because I know that the work is done in the background.

Is there a way to access the camera in between layer calls with only one camera? I know the use of double cameras and changing the clear flags, but it distorts a lot of example projects like water4 since it calls Camera.main. Since I have more than one camera, there is no real Camera.main anymore.