Complex sentence: The zone along which the needle moves, shows how much time is left untill the mechanism would be expected to cease autonomous operation, correspopndingly, when the hand leaves the zone the watch needs to be wound.
Split into simpler sentences: The zone along which the needle moves, shows how much time is left until the mechanism would be expected to cease autonomous operation. Correspondingly, when the hand leaves the zone (or stops) the watch needs to be wound.