\begin{tikzpicture}[scale=.8,my arrow/.style={decorate,decoration={markings,mark=at position 1 with {\arrow[scale=1.5]{>}};}}]
%  Define circle center, point on circle, then draw the circle
\tkzDefPoint[label={[align=left]below:\(z_0\)}](0,0){o}
\tkzDefPoint(125:2){p}
\tkzDrawCircle[color=blue](o,p); \draw (320:2.2) node{\(C\)};
% plot a point z inside the circle
\tkzDefPoint[label={[align=left]below:\(z\)}](15:1){z}
%  determine the point symmetric to z with respect to circle
\tkzDefPointBy[inversion = center o through p](z)\tkzGetPoint{z*}
\tkzLabelPoint[below](z*){\(z^*\)}
% circle radius
\draw[dashed] (o)--node[left]{\(r\)} (p);
\draw[postaction={my arrow}] (o) -- ($(o)!5cm!(z*)$);
\tkzDrawPoints[fill=red](o,z,z*)
\end{tikzpicture}