\begin{tikzpicture}[
  box/.style={draw, rounded corners=2pt, align=center, font=\small, inner sep=4pt, minimum width=3.9cm, minimum height=1cm},
  arr/.style={-{Stealth[length=2.2mm]}, semithick},
  node distance=0.8cm and 0.45cm
]
\node[box] (bulk) {\zcref{s:bulk}\\ Hermite asymptotics};
\node[box, left=of bulk] (exact) {\zcref{s:exact}\\ exact formula};
\node[box, right=of bulk] (inverse) {\zcref{s:inverse}\\ inverse bound};
\node[box, below=of bulk] (endpoint) {\zcref{s:endpoint}\\ endpoint matrix};
\node[box, below left=of endpoint, xshift=1.3cm] (one) {\zcref{s:oneinterval}\\ one interval};
\node[box, below right=of endpoint, xshift=-1.3cm] (several) {\zcref{s:severalintervals}\\ several intervals};
\node[box, below=of one] (first) {\zcref{s:firstmoment}\\ first moment};
\node[box, below=of several] (factorial) {\zcref{s:factorial}\\ proof of \zcref{t:main}};
\node[box, right=of factorial] (poisson) {\zcref{s:poisson}\\ Poisson criterion};
\draw[arr] (exact) -- (endpoint);
\draw[arr] (bulk) -- (endpoint);
\draw[arr] (inverse) -- (endpoint);
\draw[arr] (endpoint) -- (one);
\draw[arr] (endpoint) -- (several);
\draw[arr] (bulk.south west) -- (one.north);
\draw[arr] (one) -- (several);
\draw[arr] (one) -- (first);
\draw[arr] (one) -- (factorial);
\draw[arr] (several) -- (factorial);
\draw[arr] (first) -- (factorial);
\draw[arr] (poisson) -- (factorial);
\end{tikzpicture}