Post date: Mar 4, 2014 12:05:54 AM
Systems with with a zero tend to exhibit large overshoots. This is because of the derivative action the zeros cause. If (10*s+4)/(s^2+1*s+4) is the system, then the 10*s term differentiates and magnifies the response for the system without the numerator term.
If the zero happens to be in the RHP, the system may exhibit an undershoot.