The calculated distance (air line) between Az̧ Z̧a‘āyin and Dukhān is approximately 45 miles respectively 72 kilometers.
By car or train, the actual journey to Dukhān is certainly longer, as only the direct route (as the crow flies) between Az̧ Z̧a‘āyin and Dukhān has been calculated here.
Air line (approximately)
72 kilometers
39 nautical miles