Zn(OH)2 is an insoluble ppt, but can form a soluble complex ion
of tetrahydroxozincate(II) ion, in excess OH-(aq).
NaOH is stable (as Na+ has relatively low charge density), and
will not lose water to form Na2O. When excess water is evaporated
away, you will get white solid NaOH(s).
On the other hand, Zn2+ has relatively higher charge density, is
more unstable and hence Zn(OH)2 will lose water when heated to form
ZnO(s).
Zinc oxide is yellow when hot, white when cold; the yellow
colour arises from interactions in the crystal lattice, and not due
to d-d* transition, since Zn2+ has no partially filled d-orbitals
and doesn’t qualify as a transition metal.