Ground prep, foundation laying and curing take around 2 months usually. Sorry, I meant to add that, but I guess it passed my mind. If you don't let the concrete foundation cure before building on it, it will literally crumble.
My point was that in total, I don't think you gained any man-hours at all, but would incur an insane cost. Running 6 cranes wouldn't necessarily demand inefficiencies (although in reality I'd expect a lot). If you assigned an area to each crane and movement zones, you could probably get away with minimal time losses, however for tying the structure together you could never get more than a level ahead of the other cranes.
Also, you do have to admit, that there are some inefficiencies involved in running shifts back-back, and using multiple cranes.
And the Project Plan and Management on this development must have been 10x what you would have seen in a typical six-nine month building project.