To facilitate zoom lens design, a systematic zoom lens design approach, based on mixed lens modules, is proposed in this paper, which consists of paraxial lens design, lens type determination, and aberration design. During paraxial lens design, Gaussian brackets and matrix optics are adopted, with which the relationship between component interval distances and component focal lengths can be easily determined. A lens module classification model is trained, with which the lens type can be determined from its thin lens parameters. More than 80% of the lens components have been successfully classified by the classification model. Mixed lens modules, namely thin lens modules and thick lens modules, are applied for aberration design of lens components, with which the component aberrations can be easily balanced and some practical considerations, such as interval distances between lens elements and components collisions, can be handled simultaneously. At last, an example is provided, which shows the detailed procedure of zoom lens design using mixed lens modules.