$\mu$- and $\epsilon_i$-terms can be combined to read $\mu_m \hat L_m' H_u$, where $m=0,\dots,3$, $\hat L_0' = H_d$, $\hat L_{1,2,3}' = L_i$, $\mu_0 = -\mu$ and $\mu_{1,2,3} = \epsilon_i$. The $\mu_m$ term can be perturbatively rotated so that only $\mu_0$ is nonzero. This requires the rotation $\hat L' \to \hat L = R_\mu \hat L' $ with $$R_\mu =
    \begin{pmatrix}
        1 & -\frac{\epsilon_1}{\mu} & -\frac{\epsilon_2}{\mu} & -\frac{\epsilon_3}{\mu}
    \\
        \frac{\epsilon_1}{\mu} & 1 & 0 & 0
    \\
        \frac{\epsilon_2}{\mu} & 0 & 1 & 0
    \\
        \frac{\epsilon_3}{\mu} & 0 & 0 & 1
    \end{pmatrix}.$$ Implicit in this is that $\epsilon_i \ll \mu$, which follows from the fact that $\epsilon_i$ contributes to neutrino masses, as we shall see later. The rotation leaves only one bilinear between $H_u$ and a linear combination of $L_m'$, which is, of course, mostly composed of $H_d$. This rotation must also be applied to $H_d$ in the down-type quark Yukawa term, $Y_d$, and the charged lepton Yukawa coupling term, $Y_e$, see Eq. (\[W\]). The parameterization of $\lambda_{ijk}$ and $\lambda_{ijk}'$ can be read off from this rotation: $$\begin{aligned}
    \label{lambda}
    \lambda_{ijk} & = \frac{1}{2}{Y_e}_{ik}\frac{\epsilon_j}{\mu}-\frac{1}{2}{Y_e}_{jk}\frac{\epsilon_i}{\mu}
    \\
    \lambda_{ijk}' & = {Y_d}_{ik}\frac{\epsilon_j}{\mu}. \label{lambda2}\end{aligned}$$ Because the charged lepton and down quark Yukawa matrices are dominated 