"Co chtějí tamti muži?"

Translation: What do those men want?

[Vixg]

I have a doubt: which is the object of chtít, nominative or accusative?
Thank you

[BoneheadBass]

It is accusative, as the direct object of the verb. Co has the same form in both the nominative and accusative case.

[cronanas]

Are muži and mužové interchangeable?

[VladaFu]

Muži is much more common, mužové sounds strange in most non-poetic contexts. It is a complex topic with many subtleties for different words https://prirucka.ujc.cas.cz/?id=226