In my experience:
Abs. Quads. Glutes. Upper back - less than the front squat. Painful for the elbows, so, for me, not the weight, but the pain was the limiting factor.
Think of something between the front squat and the belt squat.
The interesting implementatuon would be: front squat, when the grip fails, switch to California front squat, then catch it in the zercher position, squat some more, put it on the legs and deadlift it down.
The benefit ( the major one) would be squatting without a rack. I have deadlifted it to the hips and squatted from there way before Fabio's instructions. It's a natural thing to do.
That being said, after I have got myself a squat rack, I have abandoned the zercher squat without any regrets. An exercise should not hurt.
My choice of squats is: low bar squat and front squat. Low bar is "hips up", and front squat is "chest up". High bar squat is in between. By the way - I totally get the Olympic lifters squatting high bar: closer to the front squat, and you can dump the bar back without using a rack.