Tcolorbox inside align environement

Question

I wonder if it's possible to align the coloured equal signs. I have used tcolorboxes between align environments. I doubt so but, is there a way of using tcolorboxes within an align environement? Would it be possible to tell a second align environment to resume a previous one?

\documentclass{article}
\usepackage{amsmath}
\usepackage{tcolorbox}

\newtcolorbox{AuxCalc}{
notitle,
colframe=black!75!white,
colback=black!20!white
}

\newtcolorbox{AuxCalc2}{
notitle,
colframe=black!75!white,
colback=black!10!white
}

\begin{document}

\begin{align*}
    1 &= 2 \\
    1 &= 2 \\
\end{align*}

\begin{AuxCalc}

    \begin{align*}
        14312 &= 2 \\
        1 &= 12342 \\
    \end{align*}
        
    \begin{AuxCalc2}
        \begin{align*}
            1 &= 2 \\
            1 &= 2 \\       
        \end{align*}
    \end{AuxCalc2}
    
    \begin{align*}
        11235132 &= 2 \\
        123513251 &= 2 \\
    \end{align*}
    
\end{AuxCalc}


\begin{align*}
    12341 &= 2 \\
    112512351 &= 2 \\
\end{align*}

\end{document}

Answer 1

Not a particularly attractive approach, but it amounts to studying the areas you want aligned, in search of the widest left-side component and widest right-side component. You save those components with \savewidel and \savewider. Then, for every align type environment you wish to conform to overall alignment, if it does not already possess the widest left/right elements, you call one argument from the left and/or right sides of the environment into \setwidel and \setwider, which basically places the argument in a box the "widel" or "wider" width, with proper right or left alignment.

\documentclass{article}
\usepackage{amsmath}
\usepackage{tcolorbox}

\newtcolorbox{AuxCalc}{
notitle,
colframe=black!75!white,
colback=black!20!white
}

\newtcolorbox{AuxCalc2}{
notitle,
colframe=black!75!white,
colback=black!10!white
}

\begin{document}

\newsavebox\widemathl
\newsavebox\widemathr
\newcommand\savewidel[1]{\savebox\widemathl{$\displaystyle#1$}}
\newcommand\savewider[1]{\savebox\widemathr{$\displaystyle#1$}}
\newcommand\setwidel[1]{\makebox[\wd\widemathl][r]{$#1$}}
\newcommand\setwider[1]{\makebox[\wd\widemathr][l]{$#1$}}

\savewidel{123513251}
\savewider{12342}

\begin{align*}
    \setwidel{1} &= \setwider{2} \\
    1 &= 2 \\
\end{align*}

\begin{AuxCalc}

    \begin{align*}
        \setwidel{14312} &= 2 \\
        1 &= 12342 \\% <-- HERE IS WIDEMATHR
    \end{align*}
        
    \begin{AuxCalc2}
        \begin{align*}
            \setwidel{1} &= \setwider{2} \\
            1 &= 2 \\       
        \end{align*}
    \end{AuxCalc2}
    
    \begin{align*}
        11235132 &= \setwider{2} \\
        123513251 &= 2 \\% <-- HERE IS WIDEMATHL
    \end{align*}
    
\end{AuxCalc}


\begin{align*}
    12341 &= \setwider{2} \\
    112512351 &= 2 \\% <-- HERE IS ALSO WIDEMATHL
\end{align*}

\end{document}