We present a first-principles investigation of the electronic structure, lattice dynamics, electron-phonon coupling, and superconducting properties of the hexagonal kagome-lattice compound ${\mathrm{Re}}_2\mathrm{Zr}$, in which time-reversal symmetry breaking and unconventional pairing were recently proposed. We examine whether superconductivity in ${\mathrm{Re}}_2\mathrm{Zr}$ can be explained within a conventional phonon-mediated framework by performing fully ab initio calculations within the density functional theory for superconductors. The electronic structure is characterized by a mixture of seven two- and three-dimensional Fermi surface sheets, giving rise to multiband superconductivity with many overlapping superconducting gaps. A spin-orbit-induced Van Hove singularity is identified in the density of states near $E_F$. The electron-phonon interaction is moderately strong, with a coupling constant $\lambda \simeq 0.88$. Superconducting gap calculations reveal significant anisotropy and a broad distribution of gap values across different Fermi surface sheets. Spin fluctuations introduce additional depairing effects and reduce the critical temperature from 7.7 to 6.4 K, in excellent agreement with the experimental value of 6.65 K. Taken together, our results show that the superconducting energy scale in ${\mathrm{Re}}_2\mathrm{Zr}$ can be quantitatively reproduced within a conventional phonon-mediated framework, while the resulting state exhibits pronounced multiband and anisotropic gap structure. The origin of the experimentally suggested time-reversal symmetry breaking, however, remains an open question.

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• Electron-phonon coupling
• Electronic structure
• Multiband superconductivity
• Spin-orbit coupling
• Kagome lattice
• Kagome metal
• Density functional theory