How to rescale equations formatted with 'align'? Resizebox does not work

Question

My question is similar to here as well as here , but for some reason the proposed solution, i.e. using resizebox, does not work for me.

I know that the “obvious” answer is to add more line breaks, but it really doesn't make sense for what I'm trying to do to print my dissertation using as few pages as possible (to check the testimony of the target).

Here is my MWE:

\documentclass[10pt, oneside, twocolumn, notitlepage]{book}
\usepackage{amsthm,latexsym,amssymb,amsmath, amsfonts}
\usepackage{graphicx}
\usepackage{lipsum}

\newtheorem{thm}{Theorem}[section]


\newtheorem{rem}[thm]{Remark}

\begin{document}
\lipsum[1]
%\resizebox{.9\linewidth}{!}{
\begin{align*}
\mathrm{Term_{2a}} &=\iint  \left[\nabla \phi_t(x) \cdot \nabla \phi(y) + \nabla \phi(x) \cdot \nabla \phi_t(y) \right]\  e^{-\frac{\|x-y\|^2}{d^2}} W_{l}(\phi(x))W_{l}(\phi(y)) \mathrm{\ dx \ dy} \\
&=\iint  \nabla \phi_t(x) \cdot \nabla \phi(y)  e^{-\frac{\|x-y\|^2}{d^2}} W_{l}(\phi(x))W_{l}(\phi(y)) \mathrm{\ dx \ dy} \\
\end{align*}%}
\lipsum
\end{document}

It looks like this:

Adding the resizebox {.9 \ linewidth} {!} {...} command causes the following errors (sorry that it is quite small):

Answer 1

, scalebox . -:

\documentclass[10pt, oneside, twocolumn, notitlepage]{book}
\usepackage{amsthm,latexsym,amssymb,amsmath, amsfonts}
\usepackage{graphicx}
\usepackage{lipsum}

\newtheorem{thm}{Theorem}[section]


\newtheorem{rem}[thm]{Remark}

\begin{document}
\lipsum[1]

\resizebox{.9\linewidth}{!}{
  \begin{minipage}{\linewidth}
  \begin{align*}
\mathrm{Term_{2a}} &=\iint  \left[\nabla \phi_t(x) \cdot \nabla \phi(y) + \nabla \phi(x) \cdot \nabla \phi_t(y) \right]\  e^{-\frac{\|x-y\|^2}{d^2}} W_{l}(\phi(x))W_{l}(\phi(y)) \mathrm{\ dx \ dy} \\
&=\iint  \nabla \phi_t(x) \cdot \nabla \phi(y)  e^{-\frac{\|x-y\|^2}{d^2}} W_{l}(\phi(x))W_{l}(\phi(y)) \mathrm{\ dx \ dy} \\
\end{align*}
  \end{minipage}
}

\lipsum
\end{document}