This paper presents a novel approach to develop a tuning rule for a Proportional-Integral-Retarded (PIR) controller when controlling a second-order system with unstable zeros. Particularly, we address the stability and performance issues that the right-half-plane zeros impose. With this aim, we use the \emph{multiplicity-induced-dominance} properties to achieve a partial pole placement strategy guaranteeing the stability of the closed-loop system. Through this method, we derive analytical formulas for the parameters of the PIR controller that induce a predefined algebraic multiplicity for a group of real and dominant roots, ultimately enhancing system's response. Finally, numerical examples and a simulation benchmark conducted on a switched power converter show the effectiveness of the method.