Return additional relationship data in Laravel Pivot table (Laravel 9, Inertia, Vue) - eloquent

Question

I'm in a Laravel 9 project trying to access extra relationship data in a pivot table - I'm sure this will have been answered before but the answers are confusing me more!
I have a set of courses, a set of cohorts and a set of sessions. Each course can be run multiple times (each one of these I've called an instance), with multiple sessions, and one cohort.
I've created an instances table in my database which has:
course_id
cohort_id
I have a sessions table which has data on each individual session, for example a name, a review date and review status.
I then have a pivot table called instance_sessions which looks like this:
instance_id
session_id
date
trainer_id
zoom_room_id
cohort_id
I'm not sure I need the cohort id but thats by the by :-)
My question is how can I get the relationships from this pivot table to the trainer and the zoom room?
In my instance model my relationships are setup like this:
public function sessions(){
return $this->belongsToMany(Session::class)->withPivot(['date'])
->using(InstanceSession::class);
}
public function course(){
return $this->belongsTo(Course::class);
}
public function cohort(){
return $this->hasOne(Cohort::class, 'id', 'cohort_id');
}
Session model:
function instances(){
return $this->belongsToMany(Instance::class);
}
Instance Session Model:
class InstanceSession extends Pivot
{
use HasFactory;
protected $table = 'instance_session';
protected $fillable = ['instance_id', 'session_id', 'date', 'trainer_id', 'zoom_room_id', 'cohort_id' ];
public function instance(){
return $this->belongsTo(Instance::class);
}
public function session(){
return $this->belongsToMany(Session::class);
}
public function zoomRoom(){
return $this->belongsTo(ZoomRoom::class);
}
public function trainer(){
return $this->hasOne(Trainer::class);
}
}
And my Instance Controller:
$instances = Instance::with(['course', 'cohort', 'sessions'])->get();
which returns the data to an Inertia/Vue view. I've attached an image of the data being retrieved.
Any help would be gratefully received as I'm clearly not understanding something :-)
EDIT: End goal being that I want to show on the front end all of the instances with all the sessions that belong to that instance, the date those sessions take place on, the trainer name (from trainers table) taking the session and the zoom room link (from zoom room table) for the session.