  Effective non-Hermitian Hamiltonians describing decaying systems are derived
and analyzed in connection with the occurrence of possible Hilbert space
partitioning, resulting in a confinement of the dynamics. In some cases, this
fact can be interpreted properly as Zeno effect or Zeno dynamics, according to
the dimension of the subspace one focuses on; in some other cases, the
interpretation is more complicated and traceable back to a mix of Zeno
phenomena and lack of resonance. Depending on the complex phases of the
diagonal terms of the Hamiltonian, the system reacts in different ways,
requiring larger moduli for the dynamical confinement to occur when the complex
phase is close to $\pi/2$.
