To investigate the aging mechanisms and elucidate the correlations between unstable microstructure and performance in biodegradable Zn alloys, the accelerated aging experiment was conducted on a high-performance wrought Zn−0.1Mg alloy by annealing at 200 °C for varying durations. The findings reveal that the tensile strength of the alloy rapidly and significantly declines with prolonged annealing time, decreasing from 383 MPa for the as-received alloy to 102 MPa for the alloy subjected to 1440 min of annealing. The primary factors contributing to this considerable reduction in strength are static recrystallization, grain coarsening, and dislocation annihilation. Initially, the ductility of the alloy shows fluctuations, ultimately experiencing a marked decrease after extended annealing. This decline is linked to the grain growth and heightened texture intensity, while the unusual increase in ductility observed between 30 and 120 min of annealing is likely due to the formation of twins. In addition, due to rapid grain growth and an increase in precipitates and twins, the corrosion resistance of the alloy in Hank’s solution has worsened, with the corrosion rate rising from 0.037 to 0.069 mm/a following 300 min of annealing.