According to the design drawings, this is the "Enhanced Transformable MS ZZ Gundam for the Quin Mantha, the ultimate MS for fighting Newtypes."

I previously built an HGUC ZZ Gundam
https://www.gn-app.com/posts/2cef3ba1-80c3-48ae-96b5-a5b876fb21d4
and modified it into an enhanced version. (It's not the MG that's been getting a lot of attention for its Full Armor version 💦)
The parts used for the conversion were shoulder thruster armor & connection parts, shield, waist front armor, toes & heels, backpack, and calf thrusters from another HG and an old Full Armor kit.

MSZ-010S Enhanced ZZ Gundam | 121kry's Gunpla works