How to differentiate date format?

I need to format a cell so that when I enter a date in format 6/12 it would show “december 6, 2018”, but if I enter 0 it would show “.._______”

The first one is simple - just use a date format, but how to get it to show the other outcome when the date is “0”?

[<>0]MMMM D, YYYY;"____.____._______"

See Number Format Codes.

Thank you!