The short answer is yes, but it will not work in the exact same way as with e.g. MS Word. You can gather all your refererences in EndNote/Zotero, and then export and upload them in Overleaf (the same way you upload images). You can also add references directly into your reference library in LaTeX.

There are three options for handling references in Overleaf:

Create a .bib-file and add references manually, or import directly from Oria or other databases.
Export your references from Zotero or EndNote, and import them in a .bib-file
Choose to create a file "From Zotero" in Overleaf, which produces a .bib-file that is synchronised directly with your Zotero-library (does not work with EndNote)

There are different advantages to these options, so you might want to test them out to find your preferred work method. For option 1 and 2, you can freely edit your .bib-file in Overleaf, whereas with option 3, the .bib-file is locked in Overleaf (all reference editing must be done in Zotero).

To export from Zotero, choose File --> Export library --> Format: BibLaTeX and encoding Unicode (UTF-8)

To export from EndNote choose File --> Export --> Filtype: Text file (.txt) and Output style: BibTeX Export (the first time you export you will have to select another style and then search for BibTeX Export).

Click here to see in Zotero

Click here to see in EndNote