Talk & Share PC Sound Same Time

How do I play soft music in the background and talk at the same time on Zoom?

It's for guided visualisation with clients

When I click on "share screen" and "share sound" in basic mode the mp3 music plays but my voice is muffled.
If I go to the advanced tab and select "computer audio" it won't let me check the box in the bottom left "share sound" at the same time.

How do I get round this? 

Thank you.
Device: HP Laptop. Windows 11