• Increasing Zn content in Mg–Zn–Y–Zr alloys refines recrystallized grains and improves corrosion resistance, with Mg–3Zn–0.5Y–0.5Zr showing the lowest degradation rate (4.1–6.0 mm·a−1).
• The corrosion product layer consists of Mg(OH)2, Zn(OH)2, CaCO3, and hydroxyapatite, indicating favorable surface reactions for biomedical applications.
• Electrochemical tests confirm enhanced corrosion resistance with maximum polarization resistance of 874.5 Ω·cm2 and lowest corrosion current density of 0.104 mA·cm−2 for ZW305K.
• Alloys exhibit excellent biocompatibility with cell viability >80% after 48 h, supporting their potential as biodegradable implant materials.