Well, you a working with the two opposite ends of the spectrum as far as hand-splitting difficulty goes. Ash almost splits itself (we joke that if you look at it too hard, it will split clean in two). Elm is a total pain in the butt to split: that twisted interlocking grain makes it a bit of a pain even with a hydraulic splitter.
A trick when hand-splitting large Elm: instead of trying to split it into "pie wedges" (split through the center of the log) as you would split most wood, try splitting flakes off the outside, so much of your splitting effort "sort of" follows the growth rings, rather than cutting across the rings and through the middle of the log.
Not sure if I'm describing it well or not. If you are doing what I'm saying, the remaining unsplit log will look a bit like a hexagon or octagon when you are done with the first round of splitting off flakes. If needed, go around again, making that hexagon smaller. Only when you have a relatively small core remaining do you bother trying to split it in half through the center of the log.