\begin{flalign*}
= \left(
\dots
+ c_1\,(
  e^{-x^2}
  \,(-2\,x)
)
\right) other chars that disappear
\end{flalign*}

\begin{flalign*}
= (
...
+ c_1 (
  e^{-x^2}
   (-2 x)
)
her chars that disappear
\end{flalign*}