<p>Matzhu is a novel natural raw food rich in flavonoids, polysaccharides, and other bioactive compounds; however, its potential applications in the food industry remain largely underexplored. Milk supplemented with 0%, 0.5%, 1%, and 1.5% (w/v) Matzhu was fermented using <i>Lacticaseibacillus casei</i> LC2W. The survival of bacteria and the antioxidant activity in the resulting fermented dairy products were assessed during storage and following simulated gastrointestinal digestion in vitro. Notably, the inclusion of Matzhu significantly enhanced the viable counts of <i>L. casei</i> LC2W throughout the 21-day storage period, as well as after simulated gastrointestinal digestion. Furthermore, DPPH⁺ scavenging activity of the four groups (L₀, L_0.5, L₁, and L_1.5) were 20.87%, 31.26%, 36.17%, and 40.94%, respectively. ABTS⁺ scavenging activity also increased, following a similar trend. These results suggest that dairy products treated with Matzhu exhibited markedly increased antioxidant activity compared with those without Matzhu treatment (<i>p</i> &lt; 0.05). Untargeted metabolomic analysis identified 1269 differentially expressed metabolites across 14 classes, including unsaturated fatty acids, flavonoids, amino acids, and their derivatives. These metabolites predominantly participate in linoleic acid metabolism, amino acid metabolism, flavonoid and flavonol biosynthesis pathways, and ABC transport mechanisms. Consequently, Matzhu improves the functionality of fermented dairy products by promoting the proliferation of <i>L. casei</i> LC2W, enhancing their antioxidant properties, and influencing the production of various beneficial metabolites. In conclusion, integrating Matzhu with probiotics in fermented dairy products presents an exemplary model offering numerous potential health benefits.</p>