>I suppose zãul < deus ille,
Correct.
>but why zãu here and not zeu?
zãu /z@.../ is only a variant of zeu, but (perhaps) an older one, and
still in use in almost all subdialectal regions. In stadard Romanian
(high or official style) only "zeu" is accepted. The same applies
to the compositum Dumnezãu, Dumnedzãu, Dumnezeu, Dumnedzeu
< dominus deus.
(the -dz- variants are typical only of the subdialects spoken in
the provinces of Maramuresh and neighboring Bucovina, i.e.
Northern Moldavia, as well as in the Aromanian dialect).
>Miguel Carrasquer Vidal
g