# Matrix within matrix with numbering

What is the best way to create the below matrix in LaTeX?

I tried two ways

1) using gather, pmatrix and vmatrix inside but cannot get the desired formatting

\begin{gather}
\begin{pmatrix}
\begin{vmatrix} x_{11} & x_{12} \\  x_{21} & x_{22}\\ \end{vmatrix}
\\ y \\ z\\
\end{pmatrix}
\end{gather}


2) I get the right format using two arrays but the numbering (gather) doesn't work

\begin{gather}
$\left( \begin{array}{cr} \left| \begin{array}{cr} x_{11} & x_{12} \\ x_{21} & x_{22} \end{array}\right| \\ y \\ z \\ \end{array} \right)$
\end{gather}


You shouldn't be using gather for a single equation. Anyway, the second example is wrong because you must not have $...$ inside a math display.

The image shows too wide spaces around the fences; it was probably obtained with array.

I'll present three possibilities, in order of preference. Here I use three consecutive equation environment just because they're independent examples; for groups of consecutive equations, gather or align should obviously be used in a real document.

\documentclass{article}
\usepackage{amsmath}

\begin{document}

$$\begin{pmatrix} \begin{vmatrix} x_{11} & x_{12} \\ x_{21} & x_{22} \end{vmatrix} \\ y \\ z \end{pmatrix}$$

$$\begin{pmatrix} \;\begin{vmatrix} x_{11} & x_{12} \\ x_{21} & x_{22} \end{vmatrix}\; \\ y \\ z \end{pmatrix}$$

$$\left( \begin{array}{c} \left|\begin{array}{cc} x_{11} & x_{12} \\ x_{21} & x_{22} \end{array}\right| \\ y \\ z \end{array} \right)$$

\end{document}