As a motivating solution for the Distributed Generation (DG) multi-objective optimization siting and sizing problem, this paper introduces the application of a modified nature-inspired algorithm for enhancing the performance of Electric Distribution Networks (EDN) through the integration of Hybrid Renewable Energy Resources (RERs). The Whale Optimization Algorithm (WOA), and then the Modified whale Optimization Algorithm (MWOA), have been employed in this study. The objectives are set to optimize the active power losses, the Voltage Stability, and the total costs, considering the constraints, which are represented in the DG penetration level and the DG units' operating power factor. The proposed algorithms have been applied on various benchmark IEEE test systems (30-bus and 118-bus) as small and large EDN models. The results show that the MWOA optimization technique is more effective and successful in determining the objectives in a minimum time within a minimum number of iterations.