would it be possible to use this diode to turn 5v to 3.3v for a display ? using less than 500ma
I would agree, except for the low value of the zener's knee. A zener regulator needs a bit more room to work with than the difference between 5 and 3.3V. It is just too squirrelly in that region.If he still insists, he should use a zener to drive a transistor able to handle the required current.
Anyway, LDO regulator seems the reasonable way to go.