So can Zamazenta deal with Zacian ?
Zacian with sword dance and sacred sword seem too strong against Zamaznta.
252+ Atk Mawile Sacred Sword vs. 0 HP / 4 Def Lucario: 260-308 (80 - 94.7%) -- guaranteed 2HKO
(Sacred Sword ignores Zamazenta's ability so I didn't include it)
Not a chance in hell considering Zacian outspeeds. Zamazenta can hit Zacian neutrally with either STAB, but Behemoth Bash doesn't reliably 2HKO even when Jolly and fully invested:
252 Atk Lucario Meteor Mash vs. 0 HP / 0 Def Mawile: 145-172 (44.6 - 52.9%) -- 27.3% chance to 2HKO
Close Combat gets the 2HKO, and conveniently the stat drops are ignored by Sacred Sword:
252 Atk Lucario Close Combat vs. 0 HP / 0 Def Mawile: 175-207 (53.8 - 63.6%) -- guaranteed 2HKO
But all that means is that Zacian can't switch in and facetank.