The "drag and drop" method works for both MS Word and Google Docs.
Add In-Text Citations: Hold down the shift key, select a reference from the middle pane of Zotero, and (still holding down the shift key), drag it into Word or Google Docs.
Add Bibliography: Using the CTRL key (Windows) or CMD key (Mac), select all the references you wish to include and drag them into your paper.
To add citations to your text, click on the Zotero tab to access the Zotero Word dashboard.
Start typing your paper. When you need to add a citation, click on the "Add Edit Citation" icon.
Select the appropriate style format for your paper (Zotero will only ask you once, for each document. To change this later, go to Zotero's preferences).
Next, select a reference and click "Okay" in the pop-up window that appears.
Note your citation has been inserted.
Zotero will also automatically generate a list of your references if you click on the "Add/Edit Bibliography" icon. You only need to click on this icon once. From now on, each time you add a citation, Zotero will automatically add references to your bibliography in the proper order and in the proper style format.