  The results of experimental studies of the Shubnikov-de Haas (SdH) efect in
the (013)-HgTe/Hg$_{1-x}$Cd$_x$Te quantum wells (QWs) of electron type of
conductivity both with normal and inverted energy spectrum are reported.
Comprehensive analysis of the SdH oscillations measured for the different
orientations of magnetic field relative to the quantum well plane and
crystallographic exes allows us to investigate the anisotropy of the Zeeman
effect. For the QWs with inverted spectrum, it has been shown that the ratio of
the spin splitting to the orbital one is strongly dependent not only on the
orientation of the magnetic field relative to the QW plane but also on the
orientation of the in-plane magnetic field component relative to
crystallographic axes laying in the QW plane that implies the strong anisotropy
of in-plane g-factor. In the QW with normal spectrum, this ratio strongly
depends on the angle between the magnetic field and the normal to the QW plane
and reveals a very slight anisotropy in the QW plane. To interpret the data,
the Landau levels in the tilted magnetic field are calculated within the
framework of four-band \emph{kP} model. It is shown that the experimental
results can be quantitatively described only with taking into account the
interface inversion asymmetry.
