Output TV sound to google chrome audio cast - will ST help do this?

I am sure this can be done, but not quite got my head round it, yet. I want to watch TV, Samsung smart TV and send the sound out to ceiling speakers. Because I also want to use these speakers in a group for whole house audio, where I can say Alexa or Google play Jimi Hendrix to whole house group, I am thinking of having google chrome audio connect to amp, connected to these speakers.
So, what I would like to be able to do is get the TV audio to be sent to the google chrome audio device so that it will then play via the ceiling speakers.
The TV speakers will be in the TV speaker group and also the whole house group. So when I want, I can play Hendrix whole house through all the speakers, but at other times use just the TV speakers for the TV audio.
I expect to have two google chrome audio casts and two amps connected to the two speaker sets.
So my question is, how do I get the TV audio out to the (any) google chrome cast audio so that it can play it through the speakers it is connected to?
Any advise and suggestions would be very much appreciated. I am so close that all I think I need is a nudge in the right direction.
Many thanks

No, SmartThings will not do this for you. SmartThings is a home automation platform for controlling lights and alarms and whatnot. It is not a multimedia management platform.

Thank you Ryan. I will need to look further.

Seems like you need an AVR and a Harmony.

AVR mangages the outputs of your AV devices and sends them to various inputs/outputs connected to the AVR.

The Harmony, is a universal remote that connects to ST for HA control including voice.

For instance, I have a Projector and TV. These are displays. I have 2 sets of Speakers. I have an HTPC, XB1S, PS4, Fire TV, Nvidia Shield and Echo Dot all connected to the AVR (Yamaha rx-3050).

I can tell Alexa to, Turn On Fire TV on Projector and all associated inputs and outputs are selected and ST turns on the Switch. This change can be used to trigger whatever HA I desire such as dim lights, set temp, lock doors, etc…

Alexa, Turn On Downstairs Jazz
Alexa, Turn On Alexa Podcast
Alexa, Turn On Xbox on TV

Thanks Rontalley. I think an AVR is a bit too much for the simple things that I want to achieve. I do however see that ST probably does not have a part to play in what I want. I should be able to do it more simply with google mini or DOT and setting up rooms and using google chrome audio cast.

Thanks for your ideas and suggestions.