Maintaining Zener voltage @ 0.9 of Zener voltage
Well, the answer is simple, in this case you can calculate Rload so that it forms a voltage divider circuit with Rs, the Zener won't have any effect because you can model it as an open switch when a voltage below the Zener voltage is applied to the Zener in the reverse bias.
Hence the Zener draws nearly zero current in the simulation results.
So the obtained Vout (which is equal to 0.9 * Vz) is actually from the voltage divider not the Zener charactersitics or Zener effect.