The calculated distance (air line) between Oberwinterthur (Kreis 2) and Zürich (Kreis 7) is approximately 13 miles respectively 21 kilometers.
By car or train, the actual journey to Zürich (Kreis 7) is certainly longer, as only the direct route (as the crow flies) between Oberwinterthur (Kreis 2) and Zürich (Kreis 7) has been calculated here.
Air line (approximately)
21 kilometers
12 nautical miles