Z-scheme-based hybrid [(ZnO0.40:0.60TiO2):CdO1.00]:g-C3N4] nanocomposites (NCs) were synthesized by sol-gel precipitation and thermal polycondensation methods. Microscopic FE-SEM images varied from a compact crystal-like structure to a mesoporous sheet-type structure. XRD patterns confirmed the polycrystallinity for all samples. Meanwhile, the g-C3N4 interacts extensively with Zn+2 and Cd+2. The optical bandgap increased from 2.12 eV to 2.25 eV with the addition of g-C3N4 concentration. Z-scheme [(ZnO0.40:0.60TiO2):CdO1.00]:[g-C3N4] NCs of the particular composition named ZTCG4 showed the highest photocatalytic activity and degraded the methylene blue (MB), methyl green (MG), and methyl orange (MO) to be 99.7 %, 99.8 %, and 99.9 %, respectively, under the illumination of the visible light. Mineralized factors: chemical oxygen demand (COD) and biochemical oxygen demand (BOD) achieved the maximum removal efficiencies of 89.4 % and 88.9 % for the sample g-C3N4. Prepared photocatalysts can be utilized to remove the organic pollutants from the drainage systems under visible light exposure.