gactually this ideal-probe number-tests will help many players a bit, but i think you keep most of the results in mind subconscious as you become more and more experienced..
i actually did some work, zerg tends to mine a bit slower than protoss (i assume its the drone's turning speed) and also more expansion and relatively small amount of workers is always better than the huge economical facility
I think that article is more useful for gamers than for mapmakers, but it definatly is worth a read for anyone here.
Zerg eco is such a complicated issue, I don't think any research will be useful apart from what this article already revealed.
Since zerg eco is directly tied to unit production, you can't really tell anything. It always depends on the situation of a single game.
So of course it is better to spread your drones over as many expansions as possible, but you always have to ensure that you have the right eco/hatch ratio so that you dont waste larvae (= minerals spent on hatches) or have to low production capabilities...
Well, I guess this belongs into some strategy forum and not here ;)
He will have to go VERY deep into the materia...zerg eco is just too different and complex.
(I can't think of any other RTS with a similar economy aspect... well there was a little of it in Startreck: Armada2, but that was ridiculous... I guess that's one of the things that make Starcraft so great)