[en] In this paper the exact saturation and degeneracy of the isospin bounds, in terms of the zeros trajectories (ZT) of Im N/sub i//sub j/ [N/sub i//sub j/-specific bilinear forms] are systematically discussed. The topology of the zeros trajectories and near degeneracy of the isospin bounds in the pion-nucleon scattering are investigated using the CERN-theoretic and CERN experimental solutions for the phase shifts. The interpretation of the experiments in terms of (ZT) -topology as well as certain tests for the possible isospin breaking phenomena are suggested