\documentclass{standalone}

\usepackage[european,straightvoltages]{circuitikz}

\begin{document}

\begin{circuitikz}
    \draw (0, 0) to [C=$Z_C$] (0, 2) to (2, 2) to [R=$Z_R$] (2, 0) to (0, 0);
    \draw (0, 0) to (4, 0);
    \draw (0, 2) to (4, 2);
\end{circuitikz}

\end{document}
