Me-zu cast spells as 10th-level wu jen.
They are one CR higher than go-zu. I worked them into the Org line on Homebrews, but we can change the numbers if you desire.
I'd rather the number or Me-zu was smaller than the number of Go-zu, maybe:
Organization: Solitary, ox-team (General Ox plus 4-8 go-zu oni of CR 20-21, such as go-zu oni 12th level fighters or monks) or stampede (General Ox plus 8 go-zu oni of CR 20-21 plus 10-40 standard go-zu oni and 2-4 me-zu oni of CR 20-21 plus 5-20 standard me-zu oni)
Also, there are a few minor errors.
He should have a base speed listed for when he isn't wearing heavy armour, his unencumbered land speed would be 70 ft.
Speed: 50 ft. in full plate (10 squares; base speed 70 ft.), fly 60 ft. (perfect)
The meteoric mace "has a head
mace from a lump of meteoric iron" rather than "made from".
Since you've dropped the triple auto-quicken feat Ox can't have the quickened spells listed in his tactics entry:
Combat
General ox loves to blast away hosts of lesser opponents by simultaneously casting two
meteor swarm spells, an empowered widened
meteor swarm from his meteoric mace and a quickened
meteor swarm from his sorcerer spellcasting. For worthy foes, he prefers to Dire Charge into them and unleash full attacks using his mace in combination with quickened spells – usually
implosion or
polar ray.
Revising...
General ox loves to blast away hosts of lesser opponents with an empowered widened meteor swarm from his meteoric mace or a quickened meteor swarm from his sorcerer spellcasting. For worthy foes, he prefers to Dire Charge into them and unleash full attacks using his mace.