Hi manojfarshore,
Thanks for using Zoom SDK. The behavior you are describing is not a normal Zoom client behavior so you might need to configure it. If you are using Custom UI, below is a code snippet that could make the meeting on top of the lock screen.
this.getWindow().addFlags(
WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD
| WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED
| WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
| WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON);
Hope this helps. Thanks!