An array inside breqn (dmath) breaks the line unnecessarily

Question

Please check the following minimally working example. I know dmath is not needed in this case, but I need it in my original file.

\documentclass[12pt,letterpaper]{letter}
\usepackage{array,delarray,breqn}
\begin{document}
\begin{dmath}
    y = x \begin{array}[c] ( {c} ) 2 x y \\ y^2- x^2 \end{array}
\end{dmath}
\end{document}

See how the y is alone on the line after which the line breaks to the rest of the equation? The line is still pretty empty, so why does the line break? Can I get rid of it?

Answer 1

It's not related to delarray it occurs (a bit more surprisingly) with pmatrix as well, but in either case you can hide the matrix with {..} I'd use pmatrix here.

\documentclass[12pt,letterpaper]{letter}
\usepackage{array,delarray,breqn}
\begin{document}
delarray
\begin{dmath}
    y = x {\begin{array}[c] ( {c} ) 2 x y \\ y^2- x^2 \end{array}}
\end{dmath}

pmatrix
\begin{dmath}
    y = x {\begin{pmatrix}y \\ y^2- x^2 \end{pmatrix}}
\end{dmath}
\end{document}