That's not an error starting Zotero — that's an error using the word processor plugin.
What are you actually trying to do?
Assuming you're trying to insert a citation in a document, if it works in a new document but fails in an existing document, see Troubleshooting Errors in Word Processor Documents, linked from that dialog.
What are you actually trying to do?
Assuming you're trying to insert a citation in a document, if it works in a new document but fails in an existing document, see Troubleshooting Errors in Word Processor Documents, linked from that dialog.