When evaluating zinc alloy cars (die-cast models), you must prioritize material purity (Zamak 3 or Zamak 5) to ensure structural integrity and prevent 'zinc pest' (intergranular corrosion). Key specs include scale accuracy (e.g., 1:18, 1:24, 1:64), the electrostatic spray painting quality for a smooth finish, and the level of detail in interior components (ABS plastic or PVC). For functional models, verify the smoothness of the wheel axles and the durability of opening parts like doors and hoods.