Hello @Oh_So_Black
There are many ways to do this if you are familiar with the ZBrush toolset. All have pros and cons, and no approach is necessarily better than the others. A subject like this could be:
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Modeled from low poly with ZModeler.
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Extracted from a sculpted head.
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Extruded from a sculpted head that has been retopologized to have very deliberate topology that creates the shapes you want to extrude.
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Cut apart from a sculpted head with Live Boolean.
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Panel Looped
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Some combination of the above, with the support of many other tools besides.
Your question is very broad, and will require knowledge of the wider ZBrush toolset. If you’re not familiar with these concepts, you’d be better served with a fundamental ZBrush education than a tutorial. One way or the other, you will still need the skill to either model or sculpt the shape that you want. There are probably artistically- oriented amateur tutorials on similar armor subjects available, but they won’t help you if you don’t understand the tools being used.
I suggest starting with the Getting Started section of the documentation, and then thoroughly reading the documentation for each feature you want to use. There is also the Pixologic Classroom, where many features are demonstrated.
It will be especially important to understand how to work with and create Polygroups. Remember that in ZBrush Masking = Polypaint = Polygroups. All those things can be converted to each other, and can be used to create complex polygrouping. You could, for instance, paint your mesh with polypaint, and convert that polypaint to polygroups with which to create Extracts or Panel loops.
Once you settle on an approach, we can be more helpful with more specific questions you might have.
Good luck! 