Chloride salts extracted from hazardous municipal solid waste incineration fly ash (MSWIFA) are promising candidates for ultra-high-temperature heat storage with potential economic and environmental benefits. This study explores the structural transitions, transport performance, and thermophysical properties of heavy metal-containing molten chloride salts in the MSWIFA system (NaCl-KCl-CaCl-ZnCl). The results reveal that as ZnCl content increases, the short-range order of molten salts decreases while the medium-range order enhances. At the long range, the disorder first increases before decreasing, governed by the interactions between ion clusters and their mixing degree. The structural transformation results in a linear increase in the average density from ∼ 1.44-1.58 g∙cm at 1073 K. Self-diffusion coefficients for Na, K, Ca, Zn, and Cl ions are in the range of 5.94-7.70×10, 7.26-8.35×10, 2.31-3.45×10, 2.45-3.28×10, and 4.66-5.96×10 cm/s, respectively. The melt viscosity (∼ 1.04-6 mPa∙s) follows the N-type variation trend with turning points at 5 and 15 wt% ZnCl and the thermal conductivity (∼ 0.308-0.463 W∙m∙K) follows the reverse N-type trend with turning points at 15 and 20 wt% ZnCl. Mass specific heat capacity is negatively correlated with ZnCl content, ranging from 1.03 to 0.926 J∙g∙K, while the molar entropy is positively correlated with ZnCl content, varying from 193 to 208 J∙mol∙K. The operating temperature window gradually narrows from around 410-303 K. These findings provide crucial insights for optimizing the design and performance of MSWIFA-based molten salt systems for recycling hazardous waste into useful resources making contributions to sustainable development.