If the project owner has paid for pro, all collaborators can use the pro features in the project. Zotero sync is just a .bib file that updates itself regularly

If the project owner has paid for pro, all collaborators can use the pro features in the project. Zotero sync is just a .bib file that updates itself regularly, so if you don't want to pay, you have to upload the .bib file or past the new entries manually.