Asturian dios, Portuguese deus, Galician deus, Catalan déu, French dieu, Italian dio, Romanian zeu, Sardinian déu
Oscan διωϝηις (dioweis), Umbrian di "Zeus!," Pre-Samnite δι- (di-), Marrucinian ioues, Paelignian iouiois "to the gods," Marsian iouies 'id.'
Old Irish dïe "day," Old Welsh did 'id.,' Old Breton ded 'id.,' Old Cornish det 'id.'
Old Norse Týr "Tyr," Old English Tiw (English Týr, Tuesday)
Old Church Slavonic dьnь "day," Lithuanian diẽvas, Old Prussian deiwas
Ancient Greek Zεύς (dzeys) "Zeus," Mycenaean di-we
Messapian zis "Zeus"
Sanskrit devá- "god," Old Avestan daēuua- "god (of the pre-Zoroastrian peoples)"
The expected evolution of Latin into Spanish would have been **dio. Perhaps -s was conserved due to the important role of the word and its frequent use.