Chromecast to Google Home audio group via Google Assistant

[Android Central Question]

Hello. I'm trying to develop a Google Home routine, launched via voice command to Google Assistant, to play a specific Pandora radio channel (e.g. Smooth Jazz Radio) to a specific Home Group of audio devices ("All4"). Ideally, I'd like to say "Hey Google, play jazz" where "play jazz" is the name of the Google Home routine. I'm open to any other elegant solutions but have tried every combination of Home routine commands with no success. I just want to be able to use Assistant to Chromecast a specific radio channel to specific Home Group speakers. Thanks for any advice you can offer!