Not in Zimbabwe. And the number of languages (or vernaculars) in Zambia probably are more than a dozen. I have relatives in those countries, I've been there, and I think that counts for more than a Wikipedia entry. There is a reverse correlation between the number of languages present and the economic success prevailing. They are related neighbors, by the way.

The point is that your argument is bunk. India has a vast profusion of languages and dialects---but they speak English as a common language and do so in order to get along. English itself has such a range of dialects that it is possible for people at distant ends of the language not to understand one another (as my father found out in a Scottish pub).