在 AMS + Tasks 环境中，长方程式的行分割不起作用

Question

我使用任务 + amsmath 环境（和其他几个包）创建了一个 2 列数学问题集。

代码执行没有问题。但在分步解决方案框中，我想拆分一个长表达式以提高可读性。

无法开始\split工作。所需拆分的位置由以下代码中的注释标识。

非常感谢您的帮助！

平均能量损失

\documentclass[12pt]{exam}

%\printanswers % uncomment to print solutions.
\printanswers
\renewcommand{\solutiontitle}{}
% MACROS
%Not sure all of these packages are necessary...but the 'taks package is certainly necessary
\usepackage{amsmath}
\usepackage{cancel}
\usepackage{tikz}
\usepackage{graphicx}
\usepackage{pgfplots}
\usepackage{caption} % allows captions in minipage envir (issue w/solutions envir)
\usepackage{amssymb}
\usepackage{mathrsfs}
\usepackage{framed} %box para
\usepackage{tkz-euclide}
\usepackage{multicol}
\usepackage{tasks}
\pgfplotsset{compat=1.10}
%\displaystyle for all math environments use \lim\limits for other environments
\usepackage{parskip}

\usepackage[a4paper,margin=0.5in,include head]{geometry}
%add "showframe" above arguments to show hbox overruns
\everymath{\displaystyle}

%\unframedsolutions % uncomment to remove boxes from solutions

\setlength\parindent{1em}

\pagestyle{head}
\header{Pre-Alg. D5 Exponents Review: Product and Quotient Properties }
       {}
       {03/09/20} 

\newcommand{\pagetop}{
  \makebox[\textwidth]{Name:\enspace\hrulefill}\par
  \vspace{5mm}
  %\fbox{\fbox{\parbox{6in}{
  \fbox{\fbox{\parbox{\dimexpr\textwidth-12\fboxsep-4\fboxrule}{
    \textbf {Simplify by expansion and steps shown in class. Your answer should have only POSITIVE EXPONENTS.
     \bigskip
    \\Show all work/steps on this page.}

  }}}\par
  \bigskip
  \vspace{0.25mm}
}

\settasks{after-item-skip=1em,
          after-skip=1cm,
          label-width=2em,
          item-indent=2.5em,
          label=(\arabic*),
          column-sep=2em
          }

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% -------------------------- DOCUMENT STARTS HERE-------------------- 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\begin{document}

\pagetop
\begin{tasks}
[style=enumerate](2)
% Prob #1
\task $3m^3\cdot 3m$
\begin{solutionorbox}
$3m^3\cdot 3m$

$3^1m^3\cdot 3^1m^1$

$3^1\cdot 3^1\cdot m^3\cdot m^1 $

$3\cdot 3\cdot m\cdot m\cdot m\cdot m$

$3\cdot 3\cdot m^4$

$9m^4$
\end{solutionorbox}

% Prob #2
\task $4n^4\cdot -3n^4$
\begin{solutionorbox}
$4n^4\cdot -3n^4$

$4^1 n^4 \cdot (-3)^1 n^4$

$4^1 \cdot (-3)^1 \cdot n^4 \cdot n^4$

$4 \cdot -3 \cdot n\cdot n\cdot n\cdot n\cdot n\cdot n\cdot n\cdot n$

$4 \cdot -3 \cdot n^8$

$-12n^8$
\end{solutionorbox}

%********Problems deleted for MWE********

\task $-zx^3y^3 \cdot -3x^2y^2z^3 \cdot -4xz^2$
\begin{solution}
$-zx^3y^3 \cdot -3x^2y^2z^3 \cdot -4xz^2$

$(-1)^1z^1x^3y^3 \cdot (-3)^1x^2y^2z^3 \cdot (-4)^1x^1z^2$

\smallskip
$(-1)^1 \cdot (-3)^1 \cdot (-4)^1 \cdot x^3 \cdot x^2 \cdot x^1 \cdot  y^2 \cdot z^3 \cdot y^3  \cdot z^2 \cdot z^1]$

\smallskip
\begin{split}
{}&
%************For readability in the solution box, I want the expression to split after the last x term.***

$(-1) \cdot (-3) \cdot (-4) \cdot [x \cdot x \cdot x \cdot x \cdot x \cdot x] \cdot \\
&[y\cdot  y\cdot  y\cdot  y\cdot  y] \cdot [z \cdot z \cdot z \cdot z \cdot z \cdot z]$
\end{split}

\end{solution}

% Prob #66666666666666666666
\task $2x^2y^4 \cdot -3y^4$
\begin{solutionorbox}
$2x^2y^4 \cdot -3y^4$

$2^1x^2y^4 \cdot (-3)^1y^4$

$2^1 \cdot (-3)^1 \cdot x^2 \cdot y^4 \cdot y^4$

$2 \cdot(-3) \cdot x \cdot x \cdot y \cdot y \cdot y \cdot y \cdot y \cdot y \cdot y \cdot y$

$2 \cdot(-3) \cdot x^2y^8$

$-6x^2y^8$
\end{solutionorbox}


\end{tasks}

\end{document}