In this study, ZnO-CuO heterostructures were synthesized via a green approach using Muntingia calabura leaf extract with insights into the precursor ratio for enhanced photocatalytic performance. The synthesized materials were characterized by modern analytic methods, including X-ray diffraction, Raman spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, ultraviolet-visible absorption spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry, which elucidated the presence of CuO nanospheres and ZnO semi-cuboids. Thanks to a lower bandgap of 2.24eV compared to pristine ZnO (2.82eV), better visible light absorption, and longer charge lifetime, the optimal ZC16 sample, corresponding to a Cu:Zn ratio of 1:16, achieved a hydrogen peroxide production of 350.23μM under visible light that was further increased to 478.98μM with oxygen aeration. In addition, ZC16 also demonstrated excellent photodegradation performance towards malachite green (95.82%) and tetracycline (97.78%). Disclosure into the photocatalytic mechanism of both processes revealed the significant roles of active radicals, which have proven the environmentally friendly and cost-efficient synthesis pathway of ZnO-CuO heterostructures for environmental remediation and clean energy applications.