Branch & Bound Geometric Shapes

Here is a proposal.

\documentclass{article}
\usepackage{forest}
\usepackage{mathrsfs}
\begin{document}
\begin{forest}
for tree={s sep+=3em,l sep+=1em}
 [$\mathscr{Z}$,minimum width=3cm,minimum height=1.2cm,draw,label=right:$x_2$,
    alias=n1
  [$\mathscr{Z}_{11}$,minimum width=1.2cm,minimum height=1.2cm,draw,trapezium,
    trapezium left angle=90, trapezium right angle=60,label=right:$x_2^{(1,1)}$,
    alias=n11]
  [$\mathscr{Z}_{12}$,minimum width=1.2cm,minimum height=1.2cm,draw,,draw,trapezium,
  trapezium left angle=120, trapezium right angle=90,label=right:$x_2^{(1,1)}$,
    alias=n12]
 ]
\path (n1.south)  -- (n11.north) coordinate[midway] (aux);
\draw[dashed] (current bounding box.west|-aux)--
 (current bounding box.east|-aux);
\end{forest}
\end{document}