Z-5 is the first non-abrasive polish that will eliminate swirl marks, fine scratches and spidering, without hurting the integrity of the clear coat. It does this in stages, anywhere between 1 to 3 applications. Z2 is the show car polish that lots of us here like to end with i.e Z1, Z5, Z2, Z5, Z2 because it will produce a super high wet-looking, durable gloss. Some believe that Z5, depending on the color, actually produces a better shine on their car. Ultimately you decide which one in the end is best for you. I love my Z2!!