Zoom--Using Sidecar on iPad and Mac Using Mirrored Display

Sidecar is a continuity and mirroring feature for Apple Mac and iPad. 

Note: It requires internet, Bluetooth and must meet the system requirements. 
iPad: Pro (all models), iPad 6th generation and later, iPad mini 5th generation and later and iPad Air 3rd generation or later.
Mac: MacBook Pro introduced in 2016 or later, MacBook introduced in 2016 or later, MacBook Air introduced in 2018 or later, iMac introduced in 2017 or later, or iMac (Retina 5K, 27-inch, Late 2015), iMac Pro, Mac mini introduced in 2018 or later, Mac Pro introduced in 2019 and Mac Studio.

Setup for Sidecar

Make sure you are signed in with the same ID on both devices.
Go to "System Preferences" > select "displays".
If iPad is not connected then select "Add display pop-up" > select your iPad.

Alternative: connect using 

1. Display in control center 
2. Display menu shown on the menu bar.

Zoom Set up

• Once the Zoom app is opened.
• Select the settings icon on the top right of the app > click on the general tab.
• Select the "Dual monitor button".
  
  

To screen share select the screen share arrow icon on Zoom. The iPad screen should show as a desktop 2. You can drag whatever view, slide or app you want displayed on the iPad or Mac to both screens depending on your preference. 

This link contains a video that provides visuals.