One-Loop Corrections to the Perturbative Unitarity Bounds in the $CP$-Conserving Two-Higgs Doublet Model with a Softly Broken ${\mathbb{Z}}_2$ Symmetry

We compute all of the one-loop corrections that are enhanced, $O(\lambda_i \lambda_j / 16 \pi^2)$,inthelimit$s \gg |\lambda_i | v^2 \gg M_{W}^2$,$s \gg m_{12}^2$toallthe$2 \to 2$ longitudinal vector boson and Higgs boson scattering amplitudes in the $CP$-conserving two-Higgs doublet model with a softly broken ${\mathbb{Z}}_2$ symmetry. In the two simplified scenarios we study, the typical bound we find is $\mathrm{\mid }{\lambda }_i(s)\mathrm{\mid }⪅4$.