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This graph is for the ability of a zener diode to clamp a single high energy pulse. So if the pulse is 1mS long then the diode can dissipate 2.2 Kw if the pulse is narrow, 1us its rating is 35 kW. This graph does not show the dissipation allowed for steady state use, which is normally the most useful, with the pulse rating just checked against expected interference levels.
Just to further explain, as chuckey already well clarified the meaning of the curve: This specification is relevant when the zener diode is used for transient suppression, for example to protect against temporary overvoltage spikes or similar powerful, but not-too-often happening event. The accumulated power dissipation must anyway not heat the diode too much, so one assumes a looong time between each pulse.
Above two explanations are for the zener in transient application, as a protecting device in parallel with switching device like MOSFETs. and the explanation is good....Well if you want to use zener for voltage regulation then you have to select some other zener with required Vz and sufficient current and wattage.