a reference text on how ckm matrix would appear in a part of standard model lagrangian that contains interactions with the W-plus/minus vector gauge bosons involving quarks https://arxiv.org/abs/1912.09562
Hollik also discusses ckm matrix... also worth mentioning is the interaction of fermions and higgs boson as contained in eqn(123), pp. 19, "coupling constants proportional to the fermion masses" https://arxiv.org/abs/1012.3883
so i quite get that in my own discussions here, eqn(20.10.4), or eqn(17.8)
https://foxtrotpaparomeo.wordpress.com/2023/01/11/12012023first-order-calculations-of-the-probability-amplitude-for-higgs-boson-to-electron-positron-decay/