Low-frequency vibrations (5–25 Hz) dominate the energy content of electromechanical equipment and are a primary cause of performance degradation and failure. Conventional linear isolators face an inherent trade-off between achieving a low isolation onset frequency and maintaining high static load capacity. A quasi-zero-stiffness (QZS) isolator based on an Euler curved-beam configuration is developed to address this limitation. The relationship between beam geometry and force–displacement behaviour is established, yielding approximate analytical expressions for the restoring force and stiffness. The nonlinear dynamic response is analysed using the harmonic balance method, allowing the amplitude–frequency characteristics, stability, transmissibility, and jump phenomena to be quantified. Finite element simulations and experimental tests on a molded prototype (Ra 1.6) are conducted for validation. Consistent results are obtained across theoretical, numerical, and experimental approaches. The isolator achieves an initial isolation frequency of 8.7 Hz in simulation and 9.375 Hz in experiments while supporting a static load of approximately 320 N. The proposed design provides a compact and reliable solution for low-frequency vibration isolation in electromechanical systems.