The calculated distance (air line) between Arrasate / Mondragón and Zumaia is approximately 20 miles respectively 32 kilometers.
By car or train, the actual journey to Zumaia is certainly longer, as only the direct route (as the crow flies) between Arrasate / Mondragón and Zumaia has been calculated here.
Air line (approximately)
32 kilometers
17 nautical miles