The term isn't generic in Portuguese though, is it? As with "God" (capitalized) in English, it pretty strongly identifies the Christian deity Yahweh, yes? Same w/Dio in Italian, Dios in Spanish and Dieu in French? Deus was generic in in Latin only until the Christianization of Late Latin (circa 200-500 AD). Prior to that (in Classical Latin) it was generic.
I could be wrong, but I don't think "deus" is a Latin corruption of the Greek "Zeus". My understanding is that both words simply derive from the same Proto-Indo-European root (dyeu-, "to shine). There are a great many words in both Greek and Latin which derive from this same root (and through them, the Romance languages and English, which borrows from them).