How to choose a zener diode?

Question

Electronics

It is necessary to choose a zener diode for -5V so that the stabilization current is somewhere around 5mA, and the resistance of the zener diode is less than 12 .. I can’t find such a zener diode ..
The formula for the maximum coefficient (Kmax): (Uout (1-b / 100)) / (Iout(1+c/100)+Ist)*Rd, where
b is input voltage deviation, c is input current deviation, Rd is zener diode resistance, Ist is zener diode stabilization current.
My stabilization coefficient (K) is 26.67, that is, I need Kmax to be more than 1.3 * K, and ideally even 1.5K . I
also sorted out Zener diodes for serial connection, already revised domestic reference books, and flew into online stores with Chinese zener diodes. .. some bullshit

Answer 1

Such a circuit has an order of magnitude less resistance than the zener diode participating in it. Rs is not needed, R1 ~ 600 ohms.

Answer 2

https://www.digikey.com/products/en/discrete-semic... Have you
looked here?

Answer 3

Telepaths are on vacation, as they usually say in such cases.
What task is given (circuit, input and output voltage range, load current range), what training manual do you use?
PS Formally, the problem may not have a real solution due to the fact that the nearest standard value of the stabilization voltage of zener diodes (we do not take into consideration "shunt" integral stabilizers) is 5.1 V.