If we press the volume buttons in the Xiaomi smartphone's camera app, the shutter countdown or timer is selected by default. If, for example, we would prefer a zoom function, we can change the button assignment. The following options are available to us:

Android 10 (MIUI 12.0)
Step 1:  Open the  Camera app
Step 2:  Open the  menu
Step 3:  Open the  Settings
Step 4:  Tap on  Volume buttons function
Step 5:  Choose  Shutter ,  Shutter countdown ,  Zoom  or  Volume
  1. Open the Camera app
  2. Open the menu
  3. Open the Settings
  4. Tap on Volume buttons function
  5. Choose Shutter, Shutter countdown, Zoom or Volume

Xiaomi Instructions