  The Zee model, which employs the standard Higgs scalar ($\phi$) with its
duplicate ($\phi^\prime$) and a singly charged scalar ($h^+$), can utilize two
global symmetries associated with the conservation of the numbers of $\phi$ and
$\phi^\prime$, $N_{\phi,\phi^\prime}$, where $N_\phi+N_{\phi^\prime}$ coincides
with the hypercharge while $N_\phi-N_{\phi^\prime}$ ($\equiv X$) is a new
conserved charge, which is identical to $L_e-L_\mu-L_\tau$ for the left-handed
leptons. Charged leptons turn out to have $e$-$\mu$ and $e$-$\tau$ mixing
masses, which are found to be crucial for the large solar neutrino mixing. In
an extended version of the Zee model with an extra triplet Higgs scalar (s),
neutrino oscillations are described by three steps: 1) the maximal atmospheric
mixing is induced by democratic mass terms supplied by $s$ with $X$=2 that can
initiate the type II seesaw mechanism for the smallness of these masses; 2) the
maximal solar neutrino mixing is triggered by the creation of radiative masses
by $h^+$ with $X$ = 0; 3) the large solar neutrino mixing is finally induced by
a $\nu_\mu$-$\nu_\tau$ mixing arising from the rotation of the radiative mass
terms as a result of the diagonalization that converts $e$-$\mu$ and $e$-$\tau$
mixing masses into the electron mass.
