https://web.mit.edu/2.14/www/Handouts/PoleZero.pdf
>> THE EFFECT OF ZEROS
LEFT OF THE PLANE: When the zero is located on the left of the plane (negative real number), the time response (step function sh1t) will be scaled up or down:
RIGHT OF THE PLANE: An interesting phenomenon occurs, the the derivative term, which is typically positive initially, will be of opposite sign from the scaled response term. Basically, the zero will affect the system in the opposite direction: