here is a video showing how to share screen on an ipad using Zoom - 

The basic principles are 

Open up the zoom meeting 

Go to the top of iPad screen and in the upper right click on green button - screen share 

this opens up a window 

Click screen broadcast  - then start broadcast 

to get rid of the broadcast box click anywhere 

The green button in upper right has now turned red and the other zoom participants can see your screen 

You are then able to share any application you want 

To end the screen share go back to upper right corner and click on red button - stop sharing 

You will then be back to the regular zoom meeting but have stopped the broadcast 

If you want to enable other zoom participant to be able to screen share - go to top right and click on 

participants - choose the person(s) you want to enable and this will make them co-hosts 

To end meeting - click the red button on left ( End meeting )