You've got a stereo head unit so you have left and right channels; the three speakers on the left all carry the same signal and ditto for the 3 right speakers. The split in your wiring is for fader (balance between front and rear) control; that is, you can use the fader control on the head unit to kill the sound in the rear (or alternately in the front) of the coach when necessary.
Unless you specifically want to be able to balance the front and mid coach speakers in a front to rear fashion (and then the "sweet spot" in the middle will only be in one very small area) rewiring isn't going to gain you much (especially given the work involved).
So...for your example of wanting to have music only in the bedroom; you need to access the controls on your Pioneer and change the front to rear balance (the fade) to all in the rear. Then when you turn on the unit you should only get sound out of your bedroom speakers. Since your unit is stereo you'll have left and right channels in the bedroom and it will sound good.
Hope this makes sense, lots of speakers and locations to refer to!
Les