The calculated distance (air line) between Onex and Zürich (Kreis 3) is approximately 140 miles respectively 225 kilometers.
By car or train, the actual journey to Zürich (Kreis 3) is certainly longer, as only the direct route (as the crow flies) between Onex and Zürich (Kreis 3) has been calculated here.
Air line (approximately)
225 kilometers
121 nautical miles