<p>This study provides a thorough analysis of the piecewise dynamic behavior of a quasi-zero stiffness vibration isolation model, which is based on a specific cam mechanism profile, referred to as QZSVI. The proposed model consists of a lumped mass representing the isolated object, where a cam profile provides negative stiffness, while a disk–crank–pulley mechanism supplies positive stiffness to support the load. A mathematical model of the system is developed by considering two response regimes: oscillation confined within the effective QZS region and piecewise oscillation involving transitions between the effective and non-effective stiffness regions of the cam profile. Furthermore, the damping effects associated with the hysteretic behavior of the PAM are incorporated into the dynamic model through equivalent viscous damping coefficients. An approximate analytical solution is obtained using the averaging method, and the displacement–frequency response is analyzed. Then, the displacement responses with respect to the excitation frequency are investigated for various configurative parameters through numerical simulations, and the stability characteristics of the steady-state solutions are evaluated. Furthermore, to assess the effectiveness of the proposed model, its isolation performance is compared with that of a linear counterpart and a conventional isolator with high static–low dynamic stiffness. The simulation results indicated that the proposed design can significantly mitigate the nonlinear rightward shift of the resonance peak frequency and expands the stable effective isolation region by creating quasi-zero stiffness within a specific operating range. These results are useful for the design and implementation of vibration isolators, particularly for ultra-low-frequency applications.</p>