braces on the sides of an easybmat matrix

Question

I created the following matrix with easybmat, and I would like to add at the bottom (respectively right) something like an underbrace (resp. "rightbrace") under each of the two blocks, together with a number specifying the number of columns (resp. rows) of the block. This amounts to two braces on the bottom and two on the right, and each brace should have a number below (resp. at the right) of it.

I did not find anything about that on the easybmat manual. I think I see how to do the braces with the blkarray package, but then I am not able to create the block structure of the matrix in the first place.

\documentclass{article}
\usepackage{easybmat}
\begin{document}
\[ 
M(z)= \left[
\begin{BMAT}[5pt]{c|c}{c}
\begin{BMAT}[5pt]{c:c:c}{ccccccc}
& & \\
& & \\
& & \\
v_1 & \dots & v_m \\
& & \\
& & \\
& &
\end{BMAT}
&
\begin{BMAT}{c}{c|c}
\begin{BMAT}[5pt]{c:c:c}{ccc}
& & \\
w_1(a) & \dots & w_n(a) \\
& &
\end{BMAT}
\\
\begin{BMAT}[10pt]{c}{c}
B(z)
\end{BMAT}
\end{BMAT}
\end{BMAT} 
\right]
\]
\end{document}

This is more or less what i wish:

Answer 1

For the vertical braces, you can use the bigdelim package; the horizontal braces were made using \underset and \underbrace and a "rule" of variable width and no height:

\documentclass{article}
\usepackage{amsmath}
\usepackage{easybmat}
\usepackage{multirow,bigdelim}

\newcommand*\hexbrace[2]{%
  \underset{#2}{\underbrace{\rule{#1}{0pt}}}}

\begin{document}
\[ 
M(z)= 
\begin{array}{c@{}c}
\left[
  \begin{BMAT}[5pt]{c|c}{c}
    \begin{BMAT}[5pt]{c:c:c}{ccccccc}
      & & \\
      & & \\
      & & \\
      v_1 & \dots & v_m \\
      & & \\
      & & \\
      & &
    \end{BMAT}
    &
    \begin{BMAT}{c}{c|c}
      \begin{BMAT}[5pt]{c:c:c}{ccc}
        & & \\
        w_1(a) & \dots & w_n(a) \\
        & &
      \end{BMAT}
      \\
      \begin{BMAT}[10pt]{c}{c}
        B(z)
      \end{BMAT}
    \end{BMAT}
  \end{BMAT} 
\right] 
& 
\begin{array}{l}
  \\[-8mm] \rdelim\}{4}{6mm}[$J$] \\ \\ \\[4mm]  \rdelim\}{3}{6mm}[$H$] \\ \\
\end{array} \\[-1ex]
\hexbrace{2.7cm}{m}\hexbrace{3.8cm}{n}
\end{array}
\]

\end{document}

Answer 2

Do you mean something like this?

\documentclass{article}
\usepackage{easybmat}
\begin{document}
\[ 
M(z)= \left[
\begin{BMAT}[5pt]{c|c}{c}
\underbrace{\left.\begin{BMAT}[5pt]{c:c:c}{ccccccc}
& & \\
& & \\
& & \\
v_1 & \dots & v_m \\
& & \\
& & \\
& &
\end{BMAT}\right\}6}_5
&
\begin{BMAT}{c}{c|c}
\begin{BMAT}[5pt]{c:c:c}{ccc}
& & \\
w_1(a) & \dots & w_n(a) \\
& &
\end{BMAT}
\\
\begin{BMAT}[10pt]{c}{c}
B(z)
\end{BMAT}
\end{BMAT}
\end{BMAT} 
\right]
\]
\end{document}

(If you do mean something like that, the positioning of the braces would need some adjustment, but that's easily done if this is basically what you need)