Answer : It is semiconductor diode with a low forward voltage drop and very high switching action
Answer : Yes dynamic impedance of zener diode vary.
Answer : Yes, Zener diode is a voltage regulator. Zener diode maintain constant reverse Biased Voltage. If the current is varying then also zener diode maintain constant voltage.
Description : What would cause a diode to fail?
Answer : Supply voltage beyond its limit
Description : What is the use of Schottky diode?
Answer : Schottky diode are use in SMPS, Sample and hold circuits and voltage clamping etc.