Attention hackers! Can anyone help with this sound output question?

Hey everyone, this is my first post but I joined here to see if anyone at all can help me find a solution because I have searched everywhere and havent come up with anything, so i have a weird question that I know is not possible on an unmodified android. But i need to know if there is any way to root/hack/install an app that will allow me to play music from both the aux output and bluetooth output. This is my only, last resort option. I'll explain in detail for the tech guys. I bought a Range Rover limo conversion, which has a separate front and rear sound system. The front is the stock Range rover navigation system with options for aux port (back of center console) or USB or a proprietary connector for a land rover ipod 30 pin cable. In the rear, you have a standard single DIN head unit with aux and USB input. I have tried everything to sync these systems together so I can play music from both the front and rear at the same time. The problem I'm having is, the front system has the aux port in the rear of the center console, which is missing because of the conversion's divider wall. So I'm left with ipod cable in the front and aux input in the rear. It's worth mentioning too, that I am not interested in doing any hardwiring modifications to permanently sync the systems, because, while I'd like to enjoy the sound system when IM driving the truck, if I have a driver for the night and I'm in the back I'd like to still be able to keep the rear sound system separate for when I want to roll up the divider wall and watch a movie or listen to something separately from the driver. So far, I've tried buying the land rover to 30 pin ipod adapter cable, and tried connecting a 30 pin ipod to 3.5mm aux adapter to the front and normal aux cord to the rear both going to a single Y headphone splitter. That didn't work because the front wouldn't recognize a "device" through the "ipod" option in the radio up front so it only played through the back. Currently, Ive partially solved this issue by buying a 30 pin to bluetooth adapter forthe front and an aux bluetooth adapter for the rear, and using the dual audio bluetooth function on the s9. The problem with this is, the sound is way unsynchronized, anywhere from a half second to a full second behind. I know bluetooth protocol would probably not allow the streaming to be perfectly synced. But it sounds abolsutely terrible listening to music with that mismatched sound syncronization, but I slightly prefer that over just having the front or rear playing alone. Ive played with so many adapters, fm transmitters, and bluetooth devices that I'm exhausted trying to figure this out...so is there ANY possible way for me to simply connect an aux from the rear to my phone while simultaneously streaming bluetooth to the front? First world problem, I know, but I'd really like this truck to have a synced, stock sounding sound system. Thank you!