The governing minority could not speak or understand the language of the 95% majority
Disagree with this. I am white English and am married to the daughter of a Mashona Tribal Chief. My late father in law was a minister in Ian Smith's UDI government (he was killed by Mugabe's forces in the liberation war). Ian Smith could certainly speak Shona, as can every white person I've met in Zimbabwe (and there were still plenty in July last year) even in Ballantyne Park, Harare (there were even some white checkout staff at the Spar supermarket).
Joshua Nkomo was also an MP in the federation and he was a far more effective liberation leader than Mugabe. Overall though I don't think the federation could continue, however linguistically the Shona language of Mashonaland and Manicaland in Zimbabwe and the Chewa language in Malawi (my wife can speak both) are very, very similar. The Ndebele lannguage of Matabeleland in Zimbabwe is quite different from both Shona and Chewa, being a variant of Zulu (My wife can also speak Ndebele and Zulu being raised in a mixwd part of Zimbabwe - and attending a posh private school (before independence) helps). I could see a linguistic federation possibly surviving minus Matabeleland, however I don't know anything about Zambian linguistics and how they fit with Zimbabwe and and Malawi, as Zambia is the link between the two countries (or else via Mozambique which is Swahili speaking and a very old enemy of the Mashona people).
I would agree that the federation was designed to enrich Southern Rhodesia at the expense of Zambia. Malawi (Nyasaland) has no real natural resources and is an agricultural (and very friendly country - would recommend a holiday there) country, renowned for the quality of its rice. It also has some excellent Indian restaurants.
All my my own prsonal opinion and some a bit off topic, but it is heartfelt from someone who loves Zimbabwe and its people.