Abstract: All-inorganic perovskite CsPbX₃ (X = Cl, Br, I) nanocrystals (NCs) have emerged as promising candidates for light-emitting diode (LED) displays due to their outstanding photophysical properties. However, their practical application remains hindered by poor stability and the inherent toxicity of Pb²⁺. In this study, we present a two-step heating method to synthesize CsPb_1−xZn_xBr₃ NCs with enhanced optoelectronic performance and uniform dispersion. The optimized Zn²⁺-doped NCs achieve a photoluminescence quantum yield (PLQY) of 86%, with a reduction in lattice spacing from 0.384 to 0.365 nm, attributed to increased perovskite lattice formation energy and effective surface passivation. To further improve stability, a silica (SiO₂) shell is introduced via surface modification with (3-aminopropyl) triethoxysilane (APTES), forming CsPb_0.7Zn_0.3Br₃@SiO₂ core–shell NCs. At an optimal APTES/B-site metal ion molar ratio of 1.8, the PLQY increases to 96%. The SiO₂ encapsulation significantly enhances environmental stability, with coated NCs retaining 43% of their initial photoluminescence (PL) intensity after immersion in water for 36 h, compared to only 5% for uncoated NCs. Furthermore, after ethanol treatment for 210 min, the coated NCs retain 39% of their initial PL intensity, while the uncoated counterparts retain merely 7%. The enhanced stability and luminescence performance of CsPb_0.7Zn_0.3Br₃@SiO₂ NCs make them highly promising for LED applications. White light-emitting diodes (WLEDs) fabricated using these NCs exhibit a color rendering index (CRI) of 78.2, a correlated color temperature (CCT) of 5470 K, and a luminous efficiency (LE) of 54.2 lm/W, demonstrating significant potential for next-generation display and lighting technologies.