The calculated distance (air line) between Zarautz and Saint-Jean-de-Luz is approximately 26 miles respectively 43 kilometers.
By car or train, the actual journey to Saint-Jean-de-Luz is certainly longer, as only the direct route (as the crow flies) between Zarautz and Saint-Jean-de-Luz has been calculated here.
Air line (approximately)
43 kilometers
23 nautical miles