Thats a good start there. Now about the ruthless crits,
what has help me a great deal is drawing; drawing specific body parts and understanding the anatomical structure before you go into zbrush is Extremely helpful(i often draw when i am not using ZB). It gives you a foundation to work off of, as appose to going in to ZB with limited amount of understanding of anatomy. Now i am sure you have anatomy books, so try drawing some of the body parts that you are not familiar with in diffrent angles(or draw all of them). And I 100% guarantee
you, in no time you’ll see an improvement in your work.
I am looking forward in seeing more of your work. 