From the post:
We’re delighted to announce the release of Zotero 5.0, the next major version of Zotero and the biggest upgrade in Zotero’s history. Zotero 5.0 brings many new features, as well as a huge number of changes under the hood to improve Zotero’s responsiveness and stability and lay the groundwork for other big developments coming soon. We’ll be highlighting some of the new features in upcoming posts, but for now see the changelog for more details on all that’s new.
Read more here.