You cant set ezcountry field in content type to multiple choice and set more than one default value with one transaction. You must first set multiple choice, save draft, and then you can set multiple default option.
- Go to Admin > Content type
- Click Content group
- Create new content type
- Add Country field
- Check multiple choice
- Select two country as default
- Click Publish
You can't publish - error tells You that field definition don't allow such action.
Content type published with ezcountry field with two default values.