About the Hulk's body, I'm afraid you went a bit too far into detailing it and adding muscles without having the silhouette and the volumes done right. But don't be afraid, it is extremely common when discovering Zbrush or other sculpting apps : we usually want to run before learning to walk, I did exactly the same.
What exactly is your workflow in Zbrush ? Do you start with a basemesh modelled in another software ? Do you start in Zbrush with zspheres ? Do you start from a single sphere ?
Using a 2D reference of your character from the front and from a side view can help tremendously to get volumes right : having a blueprint to follow makes shaping easier and then, when you feel the silhouette of your character is exactly like you want him to be, you can start refining him, adding the muscle details, always working from the lowest subdivision to the highest, in order. It really is like sculpting, work by little touch here and there, adding volumes, going from the biggest details to the more subtle ones.
When I look at your Hulk, I can see that you have knowledge in anatomy and that you know which muscles to emphasize. It's just that you're going too fast, not getting the base shape right and rush into detailing, which won't help and correct anything if the overall shape doesn't work.
I hope you're not getting offended by what I say, you are already quite good with faces, it is easy to tell that you've been working and observing it for a long time, it shows in your models. I think you just need to be a bit more patient when working on bodies, and spend more time on the overall shapes and volumes to achieve a good base to start from when going into detailing. I'm pretty sure you've already heard everything I said from someone else, so don't be too hard on me

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To further illustrate what I'm talking about, here's a speed sculpt from a CG artist that shows how he starts to work on the overall shape, constantly turning around his model to check and see if it looks and feel right before taking details to the next level, and doesn't hesitate to move and reshape the overall sculpt if he feels like he's losing it.
Of course, the guy is an absolute beast, it looks so easy when it is him doing it, and both of us won't be achieving those kind of result anytime soon, but it is always a good idea to check how people doing it right actually do it.
Thank you for your interest in my work, I will soon start a sculpt to make a 1/4th scale Jim Lee Storm to go alongside my other Xmen... It's been awhile I wanted to do it but I am working on other projects right now. That said, seing your work and talking with a zbrush enthusiast on this very forum just gave me the motivation to start working on Ororo real soon.