Google announced that multi-room audio is finally available for the Chromecast Audio dongle today, after several months of waiting. The new feature allows you to simultaneously cast the same audio to as many CC Audios as you have on your network. You can create groups of dongles specifically, too, which then appear on the Chromecast app for any compatible device.
The update also adds support for 96KHz/24-bit lossless audio playback, which is important for those in the audio community concerned with larger, higher numbers that are ostensibly significant in terms of quality.
Chromecast Audio Gets Multi-Room Streaming, Higher-Resolution Playback In New Update [APK Download] was written by the awesome team at Android Police.
Source: Andriod Police