The market will typically rally INTO a ZOS. The magnitude of the price move into a ZOS tells us a lot about market’s conviction and velocity.
A ZOS may occasionally take the form of a slightly declining (sagging) mkt if, after price passes through the ZOS the mkt is preparing to free-fall. In other words, “strength” can technically take the form of simply holding a range, or even sagging lower, prior to the real “weakness” which would take the form of a cascade decline.