Italian equivalent

I found "non si insegna a nuotare ai pesci" in several books about Italian proverbs, so I think that's it

I also found
l'uovo vuol sapere più che la gallina
l'uovo vuol sapere più della gallina
l'uovo ne vuol sapere più della gallina

These seem to be variations of, more or less, "the egg wants to teach the hen." It looks like it might be old fashioned. "The eggs do not teach the hen" turns up as a Russian proverb. яйца курицуне учат A book on Russian culture translated the proverb as "don't teach your granny to suck eggs" (followed by a lateral translation).

To this American, "to suck eggs" still sounds shockingly rude...not at all the sort of thing your granny would be doing...at least, not in public.

You can find all sort of suggestions that by the time our forbears got to the age of grandparenthood, they had lost most of their teeth, therefore having to subsist by sucking eggs. Which does not make a lot of sense. If Granny is indeed dentally deficient, it would be a lot easier to break the egg into a cup or bowl and drink it or eat it with a spoon. I suppose she might have sucked it out of a spoon.

Reliable sources are either silent on the origin or say it's unknown.

Indonesian eggs - telur - have the same rude connotations.