Warm Mix Asphalt (WMA) technology has emerged as a sustainable alternative to conventional hot-mix asphalt due to its ability to reduce production temperatures, energy consumption, and environmental emissions. However, lower mixing temperatures may adversely affect the binder rheology, mixture stiffness, and long-term pavement durability. Moreover, the interaction between chemical warm-mix additives and recycled polymers to simultaneously enhance the workability and mechanical performance remains insufficiently understood. This study investigated the synergistic effects of Nano-ZycoTherm and recycled low-density polyethylene (LDPE) on the rheology of asphalt binder and warm mix asphalt (WMA) mixture performance. A penetration-grade 60/70 asphalt binder was modified with 0.10 wt. % Nano-ZycoTherm, while recycled LDPE was incorporated at 1, 3, 5, and 7 wt. % of binder content. The modified binders were evaluated using conventional tests, rotational viscosity, and Dynamic Shear Rheometer (DSR) analysis. WMA mixtures were assessed using Marshall Stability, indirect tensile strength (ITS), indirect tensile stiffness modulus (ITSM), moisture susceptibility, semi-circular bend (SCB), and four-point bending fatigue tests. Statistical analyses, including Shapiro–Wilk, Levene’s, and one-way ANOVA, confirmed significant differences among the mixtures (p < 0.001). Nano-ZycoTherm reduced the binder viscosity and improved the workability, whereas LDPE increased the stiffness and elastic response. The mixture containing 7 wt. % LDPE achieved the highest mechanical performance, with an ITSM of 2.549 GPa, ITS of 1.290 MPa, and fatigue life of approximately 1.98 × 10⁵ cycles. However, SCB results indicated that 5 wt. % LDPE provided superior fracture resistance, with fracture energy of 14.8 kJ/m² compared with 12.6 kJ/m² for 7 wt. % LDPE. Considering the stiffness, fatigue resistance, fracture performance, and practical applicability, 5 wt. % LDPE was identified as the optimum modification level. The findings demonstrate that combining Nano-ZycoTherm with recycled LDPE provides an effective hybrid strategy for developing durable and sustainable WMA pavement.