From the announcement:
We’re excited to announce the availability of Zotero integration with Google Docs, joining Zotero’s existing support for Microsoft Word and LibreOffice.
The same powerful functionality that Zotero has long offered for traditional word processors is now available for Google Docs. You can quickly search for items in your Zotero library, add page numbers and other details, and insert citations. When you’re done, a single click inserts a formatted bibliography based on the citations in your document. Zotero supports complex style requirements such as Ibid. and name disambiguation, and it keeps your citations and bibliography updated as you make changes to items in your library. If you need to switch citation styles, you can easily reformat your entire document in any of the over 9,000 citation styles that Zotero supports.