You can use “Find Available PDFs” to search for full-text of multiple references at a time. Zotero will search Unpaywall for open access versions of articles as well as the University of Ottawa Library if you are on campus. Please note that this method does not always successfully retrieve all available full-text. You may still need to search for remaining full-text using the other methods above.
Select the references for which you would like to find full-text
Over one of the selected references, right-click and choose “Find Available PDFs”