  We have calculated the $W$-loop contribution to the amplitude of the decay $H
\to Z \gamma$ in the unitary gauge through the dispersion method and in the
$R_\xi$ gauge using dimensional regularization (DimReg). We show that the
results of the calculations with DimReg and the dispersion method, adopting the
boundary condition at the limit $M_W \to 0$ defined by the Goldstone boson
equivalence theorem (GBET), completely coincide. This implies that the
dispersion method obeying the GBET is compatible with DimReg. The advantage of
the applied dispersion method is that we work with finite quantities and no
regularization is required.
