In any zoom lens, individual zoom groups experience both image and pupil magnification changes during zooming. Deliberate aberration can be introduced into zoom groups to produce an overall compensatory effect over the zoom range. When using a modular design approach, in which lens groups are designed independently, one has to take into account pupil matching among zoom groups. This is analogous to the design of relay optical systems. In a zoom lens, pupil matching becomes a dynamic problem. Perfect pupil matching among zoom groups in theory cannot be maintained for a continuum of zoom positions. With the deliberate introduction of pupil aberration on the group level, compensatory effects can be obtained and a more desirable pupil match can be achieved, resulting in better stability of system image performance over the zoom range. This paper presents a systematic explanation on how pupil spherical aberration can be used in controlling residual system distortion in zoom lenses. The study involves "black box" lens modules design with the help of computer ray trace program.