Commands in \jdv denominator fails to compile.

[sjelatex]

The following code causes an issue when \vec{z} is used in the denominator only on \jdv in an \begin{align}\end{align}. It doesn't seems to appear when other derivatives defined by the package is used. Also the issue also go away in an \begin{equation}\end{equation} environment. I have not checked with other environments. Both, pdflatex, lualatex and xelatex fails to build this code.

\documentclass{article}

\usepackage{amsmath}
\usepackage{derivative}

\listfiles

\begin{document}

\begin{align}
    \jdv{f}{\vec{z}}
\end{align}

\end{document}

The issue in the log is:

! Undefined control sequence.
\mathaccentV #1#2#3#4#5->\ifmmode \gdef \macc@tmp 
                                                  {\macc@depth \@ne }\setbox...
l.12 \end{align}
                
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.

This command is not directly or indirectly used by the derivative package.

[sjelatex]

The issue also persist if I use \mathbf{z} instead

! Undefined control sequence.
\getanddefine@fonts ...p@font \let \textfont@name 
                                                  \font@name \xdef \font@nam...
l.12 \end{align}
                
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.

[sjelatex]

I have nailed it down to the var argument when it tries to insert delimiters around a variable. This probably is an expansion issue.

    \pdv[var=all]{f}{\vec{z}, y}  % does not work
    \pdv[var=1]{f}{\vec{z}, y}    % does not work
    \pdv[var=2]{f}{\vec{z}, y}    % works
    \pdv[var=none]{f}{\vec{z}, y} % works

[sjelatex]

It appears to be in \__deriv_dv_build_var_single:NNNnn at line 786

\tl_put_right:Nx #3
{
	\__deriv_insert_deninf:n {#4}
	\__deriv_insert_mskip:nn {#4} { inf_var }
	\__deriv_insert_var:NVn \l__deriv_tmpc_tl \l__deriv_tmpa_tl {#4}
	\__deriv_show_order:NT \l__deriv_tmpb_tl
	{ \__deriv_insert_ord:Nnn \l__deriv_tmpb_tl {#4} { var_ord } }
}

Something is expanding the variable, even tought I that I was already protecting the variable against expansion? The issue should also be in \__deriv_dv_build_var_multiple possible also in the _i_ versions.