### What do you see as an issue?

The documentation for zombie tasks https://airflow.apache.org/docs/apache-airflow/stable/core-concepts/tasks.html#zombie-undead-tasks is a bit abstract at the moment. There is a scope for enhancing the document by explaining how Airflow detects tasks as zombies

### Solving the problem

We can enhance the documentation by translating this query https://github.com/astronomer/airflow/blob/main/airflow/jobs/scheduler_job_runner.py#L1721 to a layman readable text in our documentation.

### Anything else

It might also help to add developer contribution steps to reproduce zombies locally.

### Are you willing to submit PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

conf.getfloat("scheduler", "parsing_cleanup_interval"),
                self._cleanup_stale_dags,
            )
        for loop_count in itertools.count(start=1):
            with Stats.timer("scheduler.scheduler_loop_duration") as timer:
                if self.using_sqlite and self.processor_agent:
                    self.processor_agent.run_single_parsing_loop()
                    
                    
                    self.log.debug("Waiting for processors to finish since we're using sqlite")
                    self.processor_agent.wait_until_finished()
                with create_session() as session:
                    num_queued_tis = self._do_scheduling(session)
                    self.job.executor.heartbeat()
                    session.expunge_all()
                    num_finished_events = self._process_executor_events(session=session)
                if self.processor_agent:
                    self.processor_agent.heartbeat()
                
                perform_heartbeat(
                    job=self.job, heartbeat_callback=self.heartbeat_callback, only_if_necessary=True
                )
                
                next_event = timers.run(blocking=False)
                self.log.debug("Next timed event is in %f", next_event)
            self.log.debug("Ran scheduling loop in %.2f seconds", timer.duration)
            if not is_unit_test and not num_queued_tis and not num_finished_events: