Incident metering will not ensure good shadow detail. In diffuse light with soft shadows, it will suffice for a good overall exposure, particularly for reversal film. But where shadows are strong they need to be spotted and evaluated then balanced with a midtone checkpoint and highlights. Essentially, with a spot meter you meter for the darkest place where you want to see detail, but not total black shadows, then a midtone checkpoint then highlight value. Average this. Only a spot meter takes into account individual illumination variations. The Zone System is an unnecessary hindrance when introduced with spot meters: many beginners are best started with metering essentials and the ZS left out until much later when skills are stepped to understanding.