> In the former case, parents choosing between 10 or so zygotes could improve the IQ of their child by 15 or more IQ points.

Well, yes—if you kill the bottom 90-93% of people ranked by intelligence, then the remainder are going to be quite smart.

Of course, that doesn't account for the possibility that there might be other good things about the children the parents never see.

And in fact, if it's true that there's a strong correlation between high intelligence and problems, then such an approach might lead to more problems than it solves.