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
