<p>Thermoelectric materials offer an exceptional opportunity to convert waste heat into electricity directly, yet their widespread application remains hindered by intrinsic brittleness and poor processability. Here, we introduce a graded ball milling strategy that fundamentally enhances the mechanical robustness and processability of YbZn₂Sb₂-based thermoelectrics. By refining grain microstructure, increasing dislocation density, and promoting intermediate-angle grain boundaries, this approach enables the fabrication of crack-free, large-size, disc-shaped, and microscale dices while maintaining excellent thermoelectric performance. Extending this strategy to a broader class of brittle Zintl compounds, including AZn₂Sb₂, AMg₂Sb₂, and ACd₂Sb₂ (A = Yb, Mg, Ca, Sr, Ba), we achieve a pre-formation cohesive energy of 9.1 eV atom⁻¹ and relatively low lattice thermal conductivity of 0.5 W m⁻¹ K⁻¹ in Yb_0.5Mg_1.3Zn_1.2Sb₂. Integrated with n-type Mg_3.1Nb_0.1Sb_1.5Bi_0.49Te_0.01, the thermoelectric module achieves a conversion efficiency exceeding 10% under a 458 K temperature gradient, operating for more than 40 hours steadily. This work establishes a scalable and versatile strategy for reconciling mechanical durability with high thermoelectric performance, paving the way for next-generation thermoelectric devices with enhanced reliability and industrial viability.</p>