code: func (api *API) ZoneSetPlan(zoneID string, plan ZonePlan) (Zone, error) {
  	zoneopts := ZoneOptions{Plan: &plan}
  	zone, err := api.EditZone(zoneID, zoneopts)
  	if err != nil {
  		return Zone{}, err
  	}
  
  	return zone, nil
  }
docs: // ZoneSetPlan changes the zone plan.