PubMed
After get the search results, check the individual references via checkboxes. In the upper right side of the screen
Click Send To, select Citation Manager and then click the Create File button.
Double-click the .nbib file that is saved to your Downloads folder on your computer, the reference should open up in Zotero. Or drag the .nbib file to Zotero collection, then open it.
EBSCO
Exporting from EBSCO to Zotero
ProQuest
After get the search results, check the individual references via checkboxes. In the upper right side of the screen, select Save, then under Export Citation
Click EndNote, Citavi, etc.
Double-click the .nbib file that is saved to your Downloads folder on your computer, the reference should open up in Zotero. Or drag the .nbib file to Zotero collection, then open it.