Zwift for Android is currently in development. We don't have a solid release date yet, but we're targeting 2018.
While you can't currently use Zwift on your Android device, it is compatible with most newer PC, Mac, and iOS devices. Apple TV is also supported. And if you are using Zwift on one of those other devices, the Zwift Companion app for Android can also be used in tandem with it for the full Zwift experience.