The calculated distance (air line) between Thalwil / Dorfkern and Winterthur is approximately 17 miles respectively 27 kilometers.
By car or train, the actual journey to Winterthur is certainly longer, as only the direct route (as the crow flies) between Thalwil / Dorfkern and Winterthur has been calculated here.
Air line (approximately)
27 kilometers
14 nautical miles