If you want to see the cores and zonations in the zircon grains, here are the possibilities. On free zircon grains (from crushing and separation) a good binocular will do and if you want more details, embed the grains in epoxy and have them polished for a flat surface then to the microscope. If on a rock thin section (ideally polished), the old petrographic microscope and an electronic microscope with cathodoluminescence capability (not all SEM has that piece) for seeing the possible cores and zonation in the zircons.

For the difference between source rocks, the color and shape of the crystals has been used for an at large origin interpretation (there are old articles about crystal shape classification vs source rock). But if the inherited zircons gets partially melted, it ends up somewhat rounded and a new layer of zircon grows on the core and the final shape of the crystal will reflect the composition of the latest host-rock. The metamorphic history is important too if the temperature and pressure are high enough to influence new growth.

So you need to look for cores in the zircons to assess their origin and zircon with no cores are quite likely to have grown in the latest melt. But you will need to know the melt/metamorphic history of the host rock area to be able to pull out the right informations.