Zotero integrates with Word and other word processors via plugins. When you export your document you can set up the citation style but not the format of the document itself. Authorea lets you do both. At any time you can export a PDF, Word or LaTeX version of your document in the style of your choice. For example your requirements may look like this: "download a one column line-numbered 12pt version with APA citations and figures positioned at the end of the document". Why is this important? If Journal X rejects your manuscript you won’t waste a second reformatting it for Journal Y. Authorea lets you export your documents to thousands of formats and citation styles in a click.