There is not much great coaching involved in beating Deiton at this level. Basic strategy is neutralize his power and annoy him with off pace shots.
That strategy is used on all levels of tennis.
Of course one has to consider the fact that there was no pressure for Kozlov in that tourney, he was not the favorite there.
Of course one also has to consider that he is two years younger. That's why there was less pressure on him. He's not supposed to win against substantially older, bigger, "far more advanced" players. Yet he did. I think that's deserving of some credit. If some guy ranked #800 in the world beats Roger Federer, I don't think it should be dismissed because he didn't have any pressure on him.
In addition, expectations actually were pretty high for Kozlov because he reached the fourth round in 2007 and had established himself as one of the elite players in the 12s.
Notice though, that right after that, in Orange Bowl, Kozlov lost second round. The reason was that now he was expected to do well and the pressure kicked in
I'm not sure how you can be so certain about that. There are other reasons why he (and Baughman and Kerznerman) could have lost, but regardless, the fact that he was such a favorite to begin with says something about him.