The host of the created Zoom Meeting depends on the settings used when scheduling the interview. By default, the host will be the Zoom Room if the interview has a room that is a Zoom Room. If the interview doesn't have a room or the room is not a Zoom Room, then it will default to the person who's scheduling the interview if that person is a Zoom user.
While this is the default, you can also manually specify who you want to be the Zoom host. You can choose from any Zoom Room or Zoom users on your account. You can specify this either on the stage scheduling preferences (if you want this Zoom host for all interviews moving forward) or during the Availability Step when scheduling a candidate if you only want it to apply to that single candidate.
In addition, you can configure the Zoom host to be the first interviewer. When this option is selected, it will prefer the first interviewer on the panel that has no other Zoom meetings during that time. This is most useful for one-on-one interviews where you want the interviewer to be the Zoom host of their own interview, but it can also be used for onsite as well so that not all interviews are being hosted by the same person.
Regardless of how it was configured, you'll be able to see who the host is when you view the schedule in InterviewPlanner.
What the host does
When it comes to the interview itself, it doesn't matter who the host of the Meeting is. This user will not need to do anything to start the Meeting, and they won't need to join the Meeting at any point.
The main reason why it's important to know who the host is is because of Zoom's limits on hosting concurrent meetings. If you are the host of a schedule, you shouldn't create any other schedules that overlap the existing one (see What is a Zoom conflict? for more information).
Why it works this way
The reason why the Zoom host is set up this way is to provide the best experience for the candidate. We create a single Zoom Meeting for the entirety of the schedule instead of creating a separate Zoom Meeting for each interview. This makes it so that the candidate has a single Zoom Meeting URL that they have to keep track of for the whole session instead of having to leave and join a new Meeting every time the interviewer changes. And with a single Zoom Meeting, it's easier to have a single person be the host for the whole duration instead of "passing on" the host status to the next interviewer.