\documentclass[]{standalone}
\usepackage{adjustbox}
\usepackage{amsmath}
\usepackage{graphicx}
\begin{document}
$\left[
\begin{array}{ccc|ccc|c}
  \ddots & ^{\scriptscriptstyle I\text{s or }Z\text{s}} &&&&&  \\
  & {\rotatebox[origin=c]{-35}{$\scriptscriptstyle XY\text{ diagonal}$}} &&& ^{\scriptscriptstyle I\text{s or }X\text{s}} && \\
  & & \ddots &&&&{\scriptscriptstyle \text{any}} \\
  &&&\ddots &  &&^{\scriptscriptstyle \text{Pauli}} \\
  & ^{\scriptscriptstyle I\text{s or }Z\text{s}} &&& {\rotatebox[origin=c]{-35}{$\scriptscriptstyle \ \ Z\text{ diagonal}$}} && \\
  &&&& ^{\scriptscriptstyle I\text{s only}} & \ddots &
\end{array}
\right]$
\end{document}