Looks like it will only do one country at a time (I have been experimenting on my own profile). So you would have to do:
{{Notables Sticker|Southern Rhodesia Notables}}
{{Notables Sticker|Zimbabwean Notables}}
However, this will place TWO 'Is Notable' stickers on the profile! My recommendation is that you put
{{Notables Sticker|Southern Rhodesia Notables}}
and just write in the other category:
[[Category:Zimbabwean Notables]]
That way, you get only one 'Is Notable' sticker, but two categories.