sync two google accounts

My colleague is able to add a Zoom link on the CEO's Google calendar using the CEO's Zoom add-on, while still having access to her own calendar and Zoom. 

When I schedule for my boss and add a Zoom link, it automatically populates from my Zoom although it is from my manager's calendar (I have full access to manager's Gcal).  How do I integrate my manager's Zoom into her gcal while keeping my own? I know it's possible since my colleague can do it but she doesn't recall how she did it, and I can't find a way around our systems.