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This paper demonstrates the preparation of ZnMn2O4 nanoparticles through thermal hydrolysis in different solvents, such as isopropanol, ethylene glycol, glycerol, and water, combined with pyrolysis. The obtained samples were characterised by using X-ray diffraction (XRD), infrared spectroscopy (FT‒IR), scanning electron microscopy (SEM), energy-dispersive X-ray mapping, nitrogen adsorption/desorption isotherms, and a vibrating sample magnetometer. The electrocatalytic activity of ZnMn2O4 nanoparticles was investigated toward the oxidation of uric acid (UA) and xanthine (XA). The ZnMn2O4-nanoparticle-modified electrode not only enhances the oxidation currents of the two purine derivatives but also successfully separates the voltammetric signals of the analytes in their binary mixture and, hence, is employed for their simultaneous determination. The factors affecting the analysis, such as pH, scan rate, linear range, detection limit, reproducibility, and interferents, were also investigated. The results show that the UA and XA limits of detection are as low as 0.55 and 1.28 µM, and the modified electrodes have satisfactory repeatability and reproducibility. The practical application of the modified electrode was demonstrated by simultaneously determining the concentrations of UA and XA in urine samples with exceptional accuracy. [ABSTRACT FROM AUTHOR]