Not liking the lineart too much
Anyway, you can eliminate the dithering, and focus more on getting the volumes down first as you have many green shades to do the job
Eliminate the blacks for the lines 'within' the body and instead try to get contrast with a dark colour -> light colour. You may want to experiment in trying ramp the greens to the purples. Dark purples are good for shadows.
Left bicep, shouldn't be like that considering the angle of his left fist, try flexing your arm at that angle to see how the muscles behave.