$$
\begin{align}
&\begin{bmatrix}
d_{11}&d_{12}&d_{13}\\
d_{21}&d_{22}&d_{23}\\
d_{31}&d_{32}&d_{33}
\end{bmatrix}
\begin{bmatrix}
x_{11}&x_{12}&x_{13}\\
x_{21}&x_{22}&x_{23}\\
x_{31}&x_{32}&x_{33}
\end{bmatrix}\\\\
&=
\begin{bmatrix}
d_{11}&0&0\\
d_{21}&0&0\\
d_{31}&0&0
\end{bmatrix}
\begin{bmatrix}
x_{11}&x_{12}&x_{13}\\
0&0&0\\
0&0&0
\end{bmatrix}\\\\
&+
\begin{bmatrix}
0&d_{12}&0\\
0&d_{22}&0\\
0&d_{32}&0
\end{bmatrix}
\begin{bmatrix}
0&0&0\\
x_{21}&x_{22}&x_{23}\\
0&0&0
\end{bmatrix}\\\\
&+