  YZ Ret is the first X-ray flash detected classical nova, and is also well
observed in optical, X-ray, and gamma-ray. We propose a comprehensive model
that explains the observational properties. The white dwarf mass is determined
to be $\sim 1.33 ~M_\odot$ that reproduces multiwavelength light curves of YZ
Ret, from optical, X-ray, and to gamma-ray. We show that a shock is naturally
generated far outside the photosphere because winds collide with themselves.
The derived lifetime of shock explains some of the temporal variations of
emission lines. The shocked shell significantly contributes to the optical flux
in the nebular phase. The decline trend of shell emission in the nebular phase
is close to $\propto t^{-1.75}$ and the same as the universal decline law of
classical novae, where $t$ is the time from the outburst.
