my camera stops working within 5 seconds after joining Zoom

If this is isolated to the Zoom app, you can try a couple things, but if it doesn't improve, you'll need to contact Zoom for help as that is not an Apple app.

1. Force Close the App --> How to force an app to close on your iPhone, iPad, or iPod touch - Apple Support
2. Force Restart your iPad:

• Pad models with Face ID: Press and quickly release the Volume Up button. Press and quickly release the Volume Down button. Then press and hold the Power button until the device restarts.
• iPad with Home button, iPhone 6s or earlier, and iPod touch (6th generation) or earlier: Press and hold both the Home and the Top (or Side) buttons until you see the Apple logo.

If neither of these solve this, contact Zoom for assistance with their app.

Zoom is not an Apple product, best you ask the app developer on their website/forum for support.

Did you try the forced restart procedure I outlined above?