<p>This study systematically investigated the stress–strain curves of a Mg-7Gd-3Y-1Zn-0.5Zr (VW73B) alloy within temperature and strain rate ranges of 440–500°C and 0.01–0.1s^-1, respectively. A strain-compensated constitutive model and three-dimensional (3D) hot processing maps were developed, combined with finite element simulation (FEM) to optimize the multidirectional forging (MDF) parameters. The reliability of both the constitutive models and the numerical simulations was further validated experimentally. The results demonstrate that the developed constitutive model accurately predicts the flow stress during hot deformation, with a mean relative error (MRE) of only 2.38%. The 3D processing maps reveal the progressive expansion of processable regions and the contraction of instability regions with increasing strain. The optimal working windows are identified as 460–480°C/0.01s^-1 under medium-strain conditions (ε = 0.4 ~ 0.6) and 450–490°C/0.1s^-1 under high-strain conditions (ε &gt; 0.8). Finite element simulation indicates that increasing the MDF passes effectively enhances strain accumulation while reducing material anisotropy, with the coefficient of variation across all directions decreasing below 0.05 after 6 passes. MDF experiments confirmed that, under optimized parameters, the VW73B billet presented minor differences in average grain size and hardness values across three-dimensional surfaces, demonstrating superior formability and microstructural homogeneity.</p>