The compliance is equal to the change of lung volume for a given pressure differential. Air moves into the nasal turbinates where air is conditioned by adding moisture and heat. Air moves into the pharynx. Here there is a connection to the guttural pouches. The pockets, bilateral, perhaps function in phonation.
Air then moves into the trachea.
The larynx is a structure of cartilage and muscle laying posterior to epiglottis. The trachea is held open by cartilaginous rings. The trachea can change diameter. The lungs are not finely dissected into lobes. Tidal volume is 5-6 L for a 450 kg horse at rest.