The word زينتهن in 24:31 is the believing women's jewelry.
It is no sin to wear jewelry (7:31, 32)
provided that what is aimed at is not متبرجات,
a showy display (24:60).
The believing women may reveal their jewelry
to the people they trust
such as their male servants who have no إربة
no need.
Surah Ta Ha
17: Now, what is this in thy right hand, O Moses?
18: It is my staff.
I lean on it,
and with it I beat down leaves for my sheep
and I meet my other need, مآرب أخرى.
By his need
did Moses mean
his sexual need?
An Nur 31:
The believing women should not reveal their zeenah
except to their own male servants who have no need.
If you were a believing woman with sexual need
and if you had a male servant who had no sexual need
would you reveal your breasts to him?
Please ask the believing women you know
if they would.