  Possible deviations from a low-energy theorem for the scattering of strongly
interacting longitudinally polarized $W$ and $Z$ bosons are discussed within a
particular scheme of electroweak symmetry breaking. The scheme (suggested
earlier by other authors in a slightly different context) is based on
spontaneous breakdown of a SU(4) symmetry to custodial SU(2) subgroup. The
physical spectrum of such a model contains a set of relatively light
pseudo-Goldstone bosons whose interactions with vector bosons modify the
low-energy theorem proven for a ``minimal'' symmetry-breaking sector. The
Goldstone-boson manifold $SU(4)/SU(2)$ is not a symmetric space. In this
context it is observed that, on the other hand, there is a large class of
models of electroweak symmetry breaking, involving groups $G$ and $H$ such that
the $G/H$ is a symmetric space and the corresponding rich multiplets of
pseudo-Goldstone bosons do not influence the canonical low-energy theorem. For
the scheme considered here, the relevant interactions are described in terms of
an effective chiral Lagrangian and tree-level contributions of the
pseudo-Goldstone boson exchanges to the vector boson scattering are computed
explicitly. A comparison with the Standard Model is made.
