Breakdown of Wszyscy wybitni dyrektorzy są nie tylko zaradni, ale i mądrzy.
być
to be
i
and
nie
no / not
ale
but
Questions & Answers about Wszyscy wybitni dyrektorzy są nie tylko zaradni, ale i mądrzy.
How does nie tylko ..., ale i ... work here, and can I use ale także instead?
The structure nie tylko ..., ale i ... (not only ..., but also ...) connects two parallel ideas to emphasize that both qualities apply. You can absolutely substitute ale i with ale także or ale również. They mean the exact same thing, though ale i is slightly shorter and very common in everyday speech.
Why are zaradni and mądrzy in the Nominative case? Shouldn't we use the Instrumental case after the verb są?
You use the Instrumental case after być (to be) when linking a subject to a noun phrase, like in Oni są wybitnymi dyrektorami (They are outstanding directors). However, when the verb być is followed only by adjectives describing the subject, those adjectives must stay in the Nominative case. Therefore, we simply use the Nominative forms zaradni and mądrzy.
The dictionary form for smart is mądry. Why does it change to mądrzy here?
Because dyrektorzy (directors) is a masculine personal noun, the adjectives describing it must take the masculine personal plural form. For adjectives ending in -ry, the r softens to rz in this specific case. This is why mądry becomes mądrzy, and similarly dobry would become dobrzy.