Op-amp based regulator with Schmitt trigger control. The concept would be to use a relatively low-power op-amp, and a lower power reference than the zener. The regulator turns on, charges up the cap, which supplies the 'load' of 800Kohms.
Once the cap is charged up, the regulator turns off until the capacitor reaches the lower threshold of the Schmitt trigger, at which point the regulator turns back on again.
Easy way to use an extra op-amp for a low-power regulator.
