Do you mean a sadwich with more than one egg inside ( kanapka z jajkami) or sandwich and eggs (kanapka i jajka )
No, not any. "with" is mostly translated as 'z + Instrumental', but for example you have also "from", which is mostly 'z + Genitive'.
"mostly", because I can't think of every possible usage of a given preposition and guarantee that it's always translated the same, prepositions differ between languages, after all ;)
Thanks for your great help :) at least now i know that "z" has more than meaing and with which case is it used. maybe with a lot of reading Polish texts would it be even more clear to figure it out with the use of preposition.
So an egg sandwich and a sandwich with eggs arent semantically necessarily the same thing. Could this be translated as either, or is one of them more correct than the other?
Seems that English preferes "an egg sandwich" while Polish goes for what means "a sandwich with egg". Both are accepted. There seems to be a single egg here, not eggs.
Egg sandwich is accepted here but a sandwich with egg is not. You need to keep consistency.