Zotero blocking use of other citation managers
Unfortunately, I need to use both Zotero and Endnote. Until very recently, when I clicked on a "cite" button at a journal website, a dialogue box popped up allowing me to choose which software to use for that reference. In the last two weeks, that choice has disappeared. I'm not sure why and don't know how to recover the option to choose the relevant software.
If that doesn't do it, you'd also want to check the file associations of your browser, but normally switching this off is sufficient.