Not an expert but I think synchronising the signals might be challenging if you hack it yourself. I know Airplay 2 has the feature to pair speakers so perhaps i

Not an expert but I think synchronising the signals might be challenging if you hack it yourself. I know Airplay 2 has the feature to pair speakers so perhaps if you can get Airplay 2 working on rpi then it might work. But in my experience the rpi experience is sub par; it was working great while it was working and then all of a sudden it stopped working.