Help/Troubleshooting, click Open Folder to open the profile folder, close TB. Open handlers.json in a text editor and search for winzip. If for some reason it's found, rename handlers.json, restart TB, open a docx attachment, and define the helper app as Word. Instead of choosing from the list, click Other.. and Browse to winword.exe.

Yay! I couldn't find help/troubleshooting open folder, so I went to appdata/roaming/thunderbird/profiles/xxxxxxxxxxx.default and found handlers.json . Sure enough there was winzip so I renamed the file. When I restarted thunderbird, I could not find winword in the list of options. I finally found it in c:\program files\microsoft office\root\office16\winword.exe and that was installed 2/15/20. It looks like this is a windows problem. I paid for automatic updates for office, and when it upgraded itself from office 15 to office 16, it did not tell the other apps about the directory change from office15 to office16. Thanks for your help. It took a bit of sleuthing, but I fixed it.