A high-efficiency PtZnCd nanozyme was screened with density functional theory (DFT) and unique d-orbital coupling features for sensitive enrichment and real-time analysis of CO-releasing molecule-3 (CORM-3). Multicatalytic sites in the nanozyme showed a high reactivity of up to 72.89 min-1 for peroxidase (POD)-like reaction, which was 2.2, 4.07, and 14.67 times higher than that of PtZn (32.67 min-1), PtCd (17.89 min-1), and Pt (4.97 min-1), respectively. Normalization of the catalytic sites showed that the catalytic capacity of the active site in PtZnCd was 2.962 U μmol-1, which was four times higher than that of a pure Pt site (0.733 U μmol-1). DFT calculations showed that improved d-orbital coupling between different metals reduces the position of the center of the shifted whole d-band relative to the Fermi energy level, thereby increasing the contribution of the sites to the electron transfer from the active center, accompanied by enhanced substrate adsorption and intermediate conversion in the catalytic process. The potential adsorption principle and color development mechanism of CORM-3 on PtZnCd were determined, and its practical application in drug metabolism was validated in vitro and in zebrafish and mice models, demonstrating that transition-metal doping effectively engineers high-performance nanozymes and optimizes artificial enzymes.