Kiro Miyazaki Instability of asymmetric nuclear matter in the extended Zimanyi-Moszkowski model (238K, PDF) ABSTRACT. We have investigated the unstable spinodal region of asymmetric nuclear matter in the extended Zimanyi-Moszkowski (EZM) model. It is found that the model produces larger spinodal region, higher upper-density boundary and maximum asymmetry, than the familiar nonlinear Walecka model. This is due to the renormalized vector-meson coupling constants in the EZM model.