... for example, because you are writing a dissertation, and want to have a bibliography at the end of each chapter.
Zotero cannot maintain multiple bibliographies in a document if you are using the Word toolbar, so you have 2 options:
1. Create a separate file for each chapter
2. or have only one file, and use the copy and paste method to create the bibliographies (perhaps have a separate collection for each chapter, and use the right mouse button to create independent bibliographies and paste them at the end of each chapter).