[Tex/LaTex] Linebreak in subequations environment

Question

I use align within subequations and this works fine for normal length equations. However I would like to break this long equation into two or three parts.

Currently I use \\ to break the long equation and my document compiles, but it doesn't give a nice result. I have seen many suggestions (multline, split, align, aligned, breqn) but I'm kind of drowning in the many possible suggestions.

This is what I have now, but as you can see equation (1a) looks like crap. (EDIT: something like this would be ideal https://i.stack.imgur.com/7YOU7.png)

\documentclass{article}
\usepackage{amsmath}

\begin{document}

\begin{subequations}
    \begin{align}
        Z^0(e^{j\omega h^0}) &= P^0_{11}(e^{j\omega h^0})\Lambda^0(e^{j\omega h^0})+P^0_{12}(e^{j\omega h^0})\mathcal{I}_{zoh}(e^{j\omega h^0})Q(e^{j\omega h})\cdot \\ \frac{1}{F}\sum_{f=0}^{F-1}P^0_{12}(e^{j\omega h^0-\frac{f}{F}\omega^0_s})\Lambda^0(e^{j\omega h^0-\frac{f}{F}\omega^0_s}) \nonumber
        \intertext{where}
        Q(\omega) &= (I-C(\omega)P_{22}(\omega))^{-1}C(\omega)
    \end{align}

\end{subequations}

\end{document}

Answer 1

I see no reasons for aligning the equals signs in the two equations, so I provide also a solution without such alignment.

The best trick, in my opinion, is to use split:

\documentclass{article}
\usepackage{amsmath}

\begin{document}

\begin{subequations}
\begin{align}
\begin{split}
Z^0(e^{j\omega h^0}) 
  &= P^0_{11}(e^{j\omega h^0})\Lambda^0(e^{j\omega h^0}) \\
  &\qquad+ P^0_{12}(e^{j\omega h^0})\mathcal{I}_{zoh}(e^{j\omega h^0})Q(e^{j\omega h})\\
  &\qquad\times \frac{1}{F}\sum_{f=0}^{F-1}P^0_{12}
     (e^{j\omega h^0-\frac{f}{F}\omega^0_s})\Lambda^0(e^{j\omega h^0-\frac{f}{F}\omega^0_s})
\end{split}
\intertext{where}
Q(\omega) &= (I-C(\omega)P_{22}(\omega))^{-1}C(\omega)
\end{align}
\end{subequations}

\begin{subequations}
\begin{equation}
\begin{split}
Z^0(e^{j\omega h^0}) 
  &= P^0_{11}(e^{j\omega h^0})\Lambda^0(e^{j\omega h^0}) \\
  &\qquad+ P^0_{12}(e^{j\omega h^0})\mathcal{I}_{zoh}(e^{j\omega h^0})Q(e^{j\omega h})\\
  &\qquad\times \frac{1}{F}\sum_{f=0}^{F-1}P^0_{12}
     (e^{j\omega h^0-\frac{f}{F}\omega^0_s})\Lambda^0(e^{j\omega h^0-\frac{f}{F}\omega^0_s})
\end{split}
\end{equation}
where
\begin{equation}
Q(\omega) = (I-C(\omega)P_{22}(\omega))^{-1}C(\omega)
\end{equation}
\end{subequations}

\end{document}