It's easy to create a bibliography from your Zotero library:

1. Select the references or collections you want to include. (Hold the control key and click to select multiple items.)
2. Right-click one of the selected items and choose Create Bibliography.
3. Choose the bibliographic style you want, and select the RTF output format.
4. Save the document to your desktop (make sure you add .rtf to the end if it doesn't show up).
5. Open the file in MS Word and re-save the item as a .docx

Or you can just drag and drop references from Zotero into your document! They'll turn into fully formatted citations. This works with any word processor including Google Docs. Change the default style under Preferences on the "gear" menu.