\documentclass{article}
\usepackage{pgf,tikz}
\usetikzlibrary{dsp,chains}
\usepackage{mathrsfs}
\usepackage[width=17cm,right=2cm,height=24cm,top=2cm]{geometry}
\usepackage{unicode-math}
\usepackage{amsmath}
\usepackage{enumitem}
\usepackage{graphicx}

\DeclareMathAlphabet{\mathpzc}{OT1}{pzc}{m}{it}
\newcommand{\z}{\mathpzc{z}}

\usepackage{xepersian}
\usetikzlibrary{arrows}
\settextfont[Scale=1.1]{Yas}
\setdigitfont[Scale=1]{Yas}
\setlatintextfont[Scale=1.1]{Times New Roman}
\setmathfont[Scale=1.1]{latinmodern-math.otf}
\linespread{1.5}
\begin{document}
\begin{center}
{\huge پردازش سیگنال‌های گسسته}

\vspace{.5cm}
{\Large تمرین 3}

\end{center}
\begin{enumerate}[label= \theenumi.]
\item
\begin{figure}[!ht]
\centering

\begin{tikzpicture}
	% Place nodes using another matrix for another picture
	\matrix (m2) [row sep=15mm, column sep=15mm, below=of m1]
	{
		%--------------------------------------------------------------------
		\node[dspnodeopen,dsp/label=left]  (m00) {$x[n]$};  &
		\node[dspnodeopen]                 (m01) {};        &
		\node[dspnodeopen]                 (m02) {};        &
		\node[dspnodeopen]                 (m03) {};        &
		\node[dspnodeopen]                 (m04) {};        &
		\node[coordinate]                  (m05) {};        \\
		%--------------------------------------------------------------------
		\node[coordinate]                  (m10) {};        &
		\node[dspnodeopen]                 (m11) {};        &
		\node[dspnodeopen]                 (m12) {};        &
		\node[dspnodeopen]                 (m13) {};        &
		\node[dspnodeopen]                 (m14) {};        &
		\node[dspnodeopen,dsp/label=right] (m15) {$y[n]$};  \\
		%--------------------------------------------------------------------
	};

	% Draw connections

	\draw[dspflow] (m00) -- (m01);
	
	\foreach \i [evaluate = \i as \j using int(\i+1)] in {1,2,3}
		\draw[dspflow] (m0\i) -- node[midway,above] {$\z^{-1}$} (m0\j);

	\foreach \i [evaluate = \i as \j using int(\i-1)] in {1,2,...,4}
		\draw[dspflow] (m0\i) -- node[midway,right] {$h[\j]$} (m1\i);
		
	\foreach \i [evaluate = \i as \j using int(\i+1)] in {1,2,...,4}
		\draw[dspflow] (m1\i) -- (m1\j);
	
	% Other elements
	\node[dspsquare, below=of m10, below=10ex]       (c0) {\upsamplertext{L}};
	\node[dspsquare,right= of c0]                    (c1) {\downsamplertext{M}};
	\node[dspfilter,right=of c1]                     (c2) {$H(\z)$};
	\node[dspmultiplier,right=of c2,dsp/label=below] (c3) {$\gamma$};
	\node[dspfilter,right=of c3,minimum size=2cm,text height=2em]
	                                                 (c4) {Weird\\ Stuff};
	\foreach \i [evaluate = \i as \j using int(\i+1)] in {0,1,...,3}
		\draw[dspconn] (c\i) -- (c\j);
\end{tikzpicture}
\caption{}
\end{figure}

\vspace{0.25cm}
\item

\vspace{.25cm}
\item

\end{enumerate}
\end{document}