The current best way is to create collections of the items in each category, then use the "Create bibliography from collection" command on each collection, then insert the resulting bibliographies manually into your word processor. Unfortunately, Zotero cannot yet create collections based on what has been cited in a given document, so you will have to create such collections manually. Equivalently, you could tag the items you are using and search for the tag, then use "Create bibliography from selected items".