  We study the possibility to reconstruct primary mass composition with the use
of combinations of basic shower characteristics, measured in hybrid
experiments, such as depth of shower maximum from fluorescence side and signal
in water Cherenkov tanks or in plastic scintillators from the ground side. To
optimize discrimination performance of shower observables combinations we apply
Fisher's discriminant analysis and give statistical estimates of separation of
the obtained distributions on Fisher variables for proton and iron primaries.
At the final stage we apply Multiparametric Topological Analysis to these
distributions to extract composition from prepared mixtures with known
fractions of showers from different primary particles. It is shown, that due to
high sensitivity of water tanks to muons, combination of signal in them with
$\xmax$ looks especially promising for mass composition analysis, provided the
energy is determined from longitudinal shower profile.
