Obtaining dynamic resistance of a zener diode in LTspice
C:\Program Files (x86)\LTC\LTspiceIV\Draft289.asc

D1 0 Vz BZX84C10L
Iz 0 Vz {iz} AC 1 0
.lib standard.dio
.ac list   1kHz
.step dec param iz  1m 40mA 20
.end
Plot V(vz)/1A


Unfortunately I was not able to upload a picture.