Z-geomancy would be a +1 Def, +1 Atk +3 SpD, +3 SpA and +3 Spe But you couldn't have a Power herb
Also, geomancy is kind of like shell smash but SpA not Atk
Here is a video of Z-Geomancy in action.
Xerneas receives the boosts you listed, but not all on the same turn. It gets +1 in every stat on the turn you use the Z-Crystal, but it still takes another turn to get the +2 in Sp. Attack, Sp. Defence and Speed. (On the first turn, Garchomp switches and Xerneas uses Z-Geomancy. On the next turn it completes Geomancy and Gyarados uses Dragon Dance.)