Scaled block matrices in LaTeX

gistfile1.tex

\newcommand{\scalemath}[2]{\scalebox{#1}{\begin{math} {#2} \end{math}}}
\newcommand{\Aprime}{\scalemath{0.5}{\begin{matrix} \Amm & \Abound \\ \zm & -\Idm \end{matrix}}}
\newcommand{\Gprime}{\scalemath{0.5}{\begin{matrix} \zm & \zm \\ \zm & \bm \end{matrix}}}
\newcommand{\Qprime}{\scalemath{0.5}{\begin{matrix} \Qm \\ \zm \end{matrix}}}

Combining the above with the Jacobian matrix as derived in \cref{sec:llg-magn-coupl}, the complete Jacobian is
\begin{equation}
  \Jm =
  \scalemath{2}{
    \begin{pmatrix}
      \Fm & \Pm & \zm \\
      \Qprime & \Aprime & \Gprime \\
      \Qm & \zm & \Amu
    \end{pmatrix}
  },
  \label{eq:16}
\end{equation}