if both the women and the men are the subject, why should men change to Acc. here?
Maybe because of the assumed "and?" But I agree that both (women and men) are in the nominative case.
'Valī' here is not accusative even though it looks that way-- when joining two parts of the same subject, you elongate the last vowel. In this same way that "ābra valā sȳri issi" means "the woman and the man are good."
Would "they are good women and men" also be correct? If not, why not?
I would like to know as well, because that's exactly what I entered...