I don’t know what you based your calculations off, but your numbers are totally wrong… also, it’s been a while since Zucken damage isn’t boosted properly by Shock effect, right now it’s the worst out of the 3 Rank7 Doppel abilities.
Whitout taking into account Zwerchau/Cleave, which is useless to account for since it boosts all of them equally:
Redel level 10 -> (368% x 14 hits) = 5152%
Zucken level 10 -> (349% x 8 hits) = 2792%
Zhornau level 10 -> (1242 x 4 hits) = 4968%
As you can see, Zucken sucks.
Also, Zhornau damage is capped, so it can’t go past 777k, total hits included, that’s why you usually don’t level it past 6, with nice transcendence and decent attribute, you’re gonna hit the damage cap easly, there is no point leveling it further.
Redel is the only skill worth maxing, hell, even Sturzhau level 5 is better than Zucken (1626% with 2 overheat against Zucken’s 2792%, one-use only)
Right now with Punish being nerfed, what Doppel lacks is AoE damage, so we’re back in spending more points in Cyclone, most of all if you didn’t follow the Shinobi route, which would have allowed you to dish out more damage in the waves.