>>58029011Behemoth Blade only appears replacing Iron Head when you give Zacian the sword that gives her extra BST and Steel type, no Z-move based on Behemoth Blade.
In fact even if you could use it offensive Z-moves boost the BP but lose the secondary effect so instead of having Crowned Zacian with a repeteable 100BP attack that gains STAB and doubles the damage against dynamaxed mons you would have a regular Zacian with a one-time weaker attack of 180BP.
Crowned Zacian (base attack of 150) using a 240BP move multiples times vs regular Zacian (base attack of 120) using a 180BP move once. You effectively just picked one of the most retardly strong pokemon ever made and made it way worse.