Need help getting stack of matrices with entry alignment across all matrix rows and columns

Question

I am trying to achieve something like the following

    ( ) text
(  )( ) text

my attempt using blkarray fails:

\documentclass{article}
\usepackage{blkarray}
\begin{document}

\begin{blockarray}{cc(cc)}
\begin{block}{cc(cc)}
  &   & 1 & 3\\
  &   & 2 & -5 \\
\end{block}
\begin{block}{(cc)(cc)}
11 & 22 & 33 & $x^2+ 1$ \\
25121 & 2 & 3 & -5\\
\end{block}
\end{blockarray}
\end{document}

• the code snippet yields extra empty matrices, which I can't figure out how to get rid of.
• the actual use case stacks matrices in both directions. The above layout is the simplest one
• I would like to use tikz to add decorations, as well as a text paragraph to the right of each level in the stack of matrices

1. The blkarray package might do what I want by e.g., adding the tikzmark package if I could figure out the extra bracket problem.
2. The nicematrix package looks promising, but I can't figure out how to add brackets to the submatrices.

Could anybody point me to a workable solution
(hopefully not too clumsy, I need to produce a lot of such figures)?
I am not tied to using any particular package...

Answer 1

Use the parentheses only in the preambles of the blocks. I added some spacing improvements:

\documentclass{article}
\usepackage{blkarray}

\begin{document}

\begin{blockarray}{cccc}
\begin{block}{cc(cc)}
  & & 1 & 3\\
  & & 2 & $ -5 $ \\
\end{block}
\noalign{\vspace{1ex}}
\begin{block}{(cc)!{\,}(cc)}
11 & 22 & 33 & $x^2+ 1$ \\
25121 & 2 & 3 & $ -5 $\\
\end{block}
\end{blockarray}

\end{document}

Answer 2

Here is a solution with {NiceArray} of nicematrix.

\documentclass{article}
\usepackage{nicematrix}

\begin{document}

$\begin{NiceArray}{cc!{\;}cc}
  & & 1 & 3\\
  & & 2 & -5 \\
\noalign{\vspace{1ex}}
11 & 22 & 33 & x^2+ 1 \\
25121 & 2 & 3 & -5 \\
\CodeAfter 
\SubMatrix({1-3}{2-4})
\SubMatrix({3-1}{4-2})
\SubMatrix({3-3}{4-4})
\end{NiceArray}$

\end{document}