To import references from a Word document, you can use the Reference Extractor tool. Note that it only works for documents whose references have already been inserted using Zotero or Mendeley and where they are still active, i.e. where they are linked and not converted to plain text!
A separate folder will be created in your Zotero library.
Dragging and dropping a reference into Zotero from Google Scholar will in most cases create a complete reference, but it should be checked like all other references that are imported.
If you already have a reference to a book and want to create a separate reference to a chapter in the book, you can easily do this by right-clicking on the book reference and selecting Create book section.
This will create a new reference where you fill in the chapter title, and there will be two fields with book author → change to author and editor.