It remains a grand challenge to develop electrocatalysts with simultaneously high activity, long durability, and low cost for the oxygen evolution reaction (OER), originating from two competing reaction pathways and often trade-off performances. The adsorbed evolution mechanism (AEM) suffers from sluggish kinetics due to a linear scaling relationship, while the lattice oxygen mechanism (LOM) causes unstable structures due to lattice oxygen escape. We propose a MoZnFeCoNi high-entropy alloy (HEA) incorporating AEM-promoter Mo and LOM-active Zn to achieve dual activation and stabilization for efficient and durable OER. Density functional theory and chemical probe experiments confirmed dual-mechanism activation, with representative Co-Co†-Mo sites facilitating AEM and Zn-O†-Ni sites enhancing LOM, resulting in an ultralow OER overpotential (η10 = 221 mV). The multielement interaction, high-entropy structure, and carbon network notably enhance structural stability for durable catalysis (>1500 hours at 100 mA cm-2). Our work offers a viable approach to concurrently enhance OER activity and stability by designing HEA catalysts to enable dual-mechanism synergy.