Abstract: Flexible zinc–air fuel cells have great potential for powering wearable electronic devices owing to their high safety, high theoretical energy density, and environmental friendliness. In conventional sandwich-structured cells, tensile deformation can directly impose stress on the electrodes, which may damage the conductive network of the electrodes. In contrast, island–bridge-structured cells can mitigate this problem through their structural advantages. In this study, a multiphysics coupling model of flexible zinc–air fuel cells was established by considering charge conservation, electrochemical reactions, gas-phase oxygen transport, ion diffusion, and solid mechanical deformation. The discharge performances of conventional sandwich-structured cells and island–bridge-structured cells were compared. First, a baseline model based on the sandwich structure was developed to analyze the current density, oxygen volume fraction, and concentration polarization caused by OH? consumption and Zn(OH)42? accumulation. The discharge behaviors of the sandwich and island–bridge structures were then further compared. The results show that the sandwich-structured cell exhibits a higher initial current density but a faster decay, whereas the island–bridge-structured cell shows a lower initial current density but maintains a more stable current output during long-term discharge. Concentration-field analysis indicates that ion transport and product accumulation in the island–bridge structure exhibit obvious localization, and the hydrogel bridge region and island–bridge junctions are key regions affecting mass-transport stability. Finally, different stretch ratios were applied to the island–bridge structure to investigate the effect of mechanically induced deformation on cell discharge performance. The results show that the island–bridge structure can concentrate most of the mechanical deformation in the hydrogel region, thereby reducing deformation in the active electrode regions. Within a certain stretching range, the constant-voltage discharge curves under different stretch ratios show only slight differences, indicating that this structure has good mechanical adaptability and electrochemical output stability. This study provides theoretical guidance for the structural design, mass-transport optimization, and flexible-electrode matching of stretchable zinc–air fuel cells.