Well, thanks for the second point about converting files to zips.

But for the first point,
What I meant was

1. Create a .dotm file
2. Open the .dotm file (itself) (right-click the file, click "Open")
3. Go to VBE
4. Under the Project panel, in the TemplateProject section, enter some codes whatever
5. Save the .dotm file
6. Close the .dotm file
7. Open the .dotm file (itself) again (right-click the file, click "Open")
8. Go to VBE
9. The codes disappear

I don't know why the codes have disappeared.