Yeah, Zidane is "Zidane" unless it's non-English European scripts, which have various name differences in various games. For Vivi, the last name "Ornitier" was used in early NA releases (in the manual only, I believe), but switched to "Orunitia" later. According to who I asked, it's given as "Ornitier" in English/'Romaji' in FFIX's official guidebook. Same thing for "Freija", which I only asked about because I remember running across some discrepancy on it before.
Now, FFTA2's "Adelle"... If the Japanese wallpapers are to be believed, she's just "Adel" there, but I don't know of any surname that'd eliminate any need for qualifiers.