Can someone please tell me how to zoom with the goggles on when linked to the Mavic. The 5d button doesn't work the zoom when connected to the goggles

This won't work. Whenever you are using the goggles, the 5D (and C1/C2) buttons are dedicated to the goggles and won't do the functions you have assigned to them.

Found the answer  on page 7 of the user manual under "function key"

Just as a hint: I had the same problem - but in the 'Head Tracking Gimbal' mode: In this mode, the FunctionKey is not working, not for focus, nor for zoom.

I tried to use a workaround to use the Zoom with "Head Tracking Gimbal" mode: But If Ifirst switch the mode off, then set up the focus/zoom with the FunctionKey and then  activate the "Head Tracking Gimbal" mode again, there seem's to be  software bug: The Focus-Cross is not displayed correctly, it is not  cleared when moving the head and leaves relicts on the screen  everywhere.