According to the modeler, he just redesigned some parts, kitbashed, made a custom weapon then detailed them up.
(Source)
HGUC ZERO-SHIKI ver.Dree [Hyaku-Shiki Revive Custom Build]
Posted inCustom Custom Color Scheme Kitbash
Posted inCustom Custom Color Scheme Height Extension
Posted inCustom Custom Color Scheme Kitbash
Posted inCustom Custom Color Scheme Kitbash