It used to be the more you have, the more likely it is that there will be optical distortions, colour fringing, chromatic aberration, etc in your picture. That's why the early zooms, with their complex optical structure, are always lousier than the much simpler prime lenses, which is also why prime lenses are usually very sharp and crisp.
However nowadays, with the introduction of wildly exotic elements, this may no longer be true. Some zooms are equal, or better to primes, but of course, you pay the price accordingly.