In answer to your question
takleg, I don't really know! The answer though, may lie in looking at other sports.
Genetically you can consider the case of rugby and the Australasia teams - Samoa, Tonga & Fiji who are naturally stronger, fitter, faster & bulkier, but hardly execute as well as teams like Eng&France! In terms of
diet, the Kenyans&Ethiopians (mostly originating from poor, rural backgrounds) don't benefit from the same quality as most Europian countries, but have more stamina, endurance & dominate long distance running. American sports have proven that
race has got nothing to with it because in the NFL, NBA & MLB, we've got a fare share of Whites who were dominant & record breaking, something Blacks have since replicated en masse once those sports were opened up to them. The only odd thing is sprints where Blacks are way ahead, but sprints also answer one thing
physique doesn't always have everything to do with it, as tall, short, broad&muscular, plus slim individuals have at different times held the 100m record!
So it leaves one thing
money! With money you receive superior education in the form of enlightenment. Through things which your family can afford - magazines, TV, attending live matches etc, you are aware of the kind of targets you need to reach at an early age i.e. pace, range of shorts, milestones - all of which serves to spare you on! Secondary to that is the superior form of equipment, coaching and training that give you the edge in the sense that you execute better, which complements your abilities whether you're naturally talented or not. A combination of both things things tends to make you more confident and better placed to back yourself - hence better results! That for me is the key/direct difference money brings - not diet, physique etc!
The reson why South African Whites haven't excelled as well as Zimbabwean Whites, is due to those benefits being spread across a wider range of people, in turn increasing higher chances of the likes of Donald & de Lange filtering through!
Perhaps we don't have that many guys who bowl quick because they've had to hold back during most of their development years. I was very quick, but(along with some of my peers), couldn't bowl fast half the time because most of the kids we played with(Black&White) didn't have pads&helmets - unfortunately I wasn't too keen on someone's sweat all over my pads - some guys were quite comfortable to rock up with just shorts on, at times minus shoes! Broken bloody nose, fractured fingers, shins etc were commonplace. So there's another reason for you to back up the money issue - we couldn't afford pads!
The core active cricket playing population of Zimbabwean is really less than 10 years. Just like Blacks in America you can expect to see a vast difference from about 2020 onwards. The same happened to for example India which had a transformation, mostly restricted to batting&spin - all which happened before the gowth of the Indian economy, but years after their invovelment in cricket. Zimbabwe will be different in the sense that African tend to have more stamina than subcontinent people, so in place of spin, you can add pace attacks to our potential future strenghts!
We might not have produced express pace, but we have produced pretty quick bowlers in this order:
1.Olonga, 2.Friend, 3.Watambwa, 4.Nicolson, 5.Blignaut, 6.Elton, 7.Jarvis, 8.Shingi 9.Mpofu, 10.Chatara
The top 3 could bowl quick all day. Nicolson ahowed he's capable. Blignaut could bowl consistently quick once in a while, but Elton&Jarvis fall in the same category because at their best they are/were mostly 138-142kph, which they can't/couldn't sustain - Elton at his quickest was far more threatening&aggressive than Jarvis - bouncy zipping balls. Mpofu
has bowled 149kph before, but in truth him and Shingi cannot bowl as fast as this pair, mainly around the 136-138kph mark, except they can sustain that pace for longer, while others dip embarassingly. Chatara is unproven, but I think he'll be in the top 5. Aliseni is a myth! Streak settled into a 128-132 mark far too early in his career, frankly, I think he got away with murder because of the swing reputation he built up!