\usepackage{fitch}
\usepackage{amsmath}

\begin{document}
$\Large\begin{nd}
  \hypo {h} {(P\implies R)\land (Q\implies R)}
  \open
    \hypo {pq} {P\lor Q}
    \open 
      \hypo {p1} {P}
      \have {p2} {P\implies R} \ae{h}
      \have {p3} {R}           \ie{p1,p2}
    \close
    \open 
      \hypo {q1} {Q}
      \have {q2} {Q\implies R} \ae{h}
      \have {q3} {R}           \ie{q1,q2}
    \close
    \have {r} {R}              \oe{pq,p1-p3,q1-q3}
  \close
  \have {e} {P\lor Q\implies R}\ii{pq-r}
\end{nd}$
\end{document}
