... for instance because you are writing a thesis, and would like to have a bibliography at the end of each chapter.
Zotero can not maintain several bibliographies in one document if you use the Word toolbar, so there are 2 options:
1. Either create a separate file for each chapter
2. or have only one file, and use the copy and paste method to create the bibliographies (maybe 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).