Zotero offers word processing plugins for Word and OpenOffice. The plugin adds a Zotero toolbar to your word processor so you can add citations as you write.
The toolbar looks different on different operating systems and versions of Word. Mousing over the toolbar will pop up each button's function.
It's easy to create a bibliography from your Zotero library. This method works with any word processor (or anywhere you can paste text).
Zotero has some Annotated bibliography options.
Google Docs support is part of the Zotero Connector for Chrome, Firefox, Edge, and Safari. You must have the Zotero standalone program also downloaded for the Google Docs integration to function.
The Zotero Connector adds a Zotero menu to the Google Docs interface, as shown in this help page:
Zotero comes with the most common bibliographic styles, but you can download many more.