If you're going to use Zotero to create citations, one vital step you need to do after adding an item to your Library is to ensure that it has all the correct citation information and the information is formatted correctly. All Zotero does when creating a citation is slot the information in the correct location for the citation format. So if the journal title is missing, if the title is miscapilitized, or the author's name is in all caps then that's how it will appear in the citation as well.
It typically only takes a few moments to check that the information is correct and it's time well spent because this ensures that Zotero will output a perfect citation for you every time.