A series of antimony zinc borate glasses with general composition (75?x)B?O?·10ZnO·10Sb?O?·5Li?O·xM?O (M = Li, Na, K; x = 0, 5, 10, 15 mol%) were synthesised by the conventional melt-quenching technique and characterised using FTIR, Raman spectroscopy, and ultrasonic velocity measurements. The infrared spectra reveal the coexistence of BO? trigonal units and BO? tetrahedral units, whose relative populations are governed by the alkali field strength. A rigorous mathematical framework employing Makishima–Mackenzie equations, elastic modulus tensors, and Smedskjaer network connectivity models is applied to correlate the spectral peak shifts with macroscopic mechanical parameters—Young’s modulus (E), bulk modulus (K), shear modulus (G), and Poisson’s ratio (?). The N? structural parameter computed from FTIR deconvolution shows a linear correlation (R² = 0.987) with the elastic modulus. Results confirm that Li?O-doped compositions exhibit superior mechanical rigidity due to enhanced network cross-linking through Li? ion bridging.