Zotero to Overleaf Local Sync by vantezzen

Zotero Better-BibTex to Overleaf Local Sync allows you to locally synchronize your Zotero bibliography to Overleaf using the Better BibTex addon.

It will add a new entry "From Better Bibtex" when creating a new file and allows you to update the file from inside the editor.

This extension is open source: https://github.com/vantezzen/zotero-better-bibtex-to-overleaf