Using Substance Painter I could easily gauge the look of the mossy areas, before scattering Megascans moss on top with XGen.

Base Mesh with Displacement & Normal Maps.

highres sculpt for comparison with below. Note the sharp edges get lost e.g. the damaged corner

3 subdivisions with autobump seems to be sweet spot. But still not happy with the overall softening & bloating.

Testing different subdivision settings for the displacement map.

Sculpt vs base mesh.

Damage pass in Zbrush - mostly alphas, trimed edges and a bit of NoiseMaker.

Base Mesh

Rather than trying to model the legs in maya, I just used booleans in Zbrush with simple shapes and zremeshed the result.

Blockout