Oops, my mistake--the brackets should be parentheses. So Kp = (Z)/((X)(Y)), where (Z) equals the partial pressure of Z, (Y) equals the partial pressure of Y, and (Z) equals the partial pressure of Z. So If pressure is increased, the reaction shifts to the left and (X) and (Y) decrease & (Z) increases, which at least appears to cause Kp to increase overall. I'm not sure where the total pressure term is?
Again, big thanks!