This model is based on an excellent concept by Furio Tedeschi. The process for creating this model is pretty simple. I start with a rough sculpt of the features, then use retopology and the Zmodeler brush to create pieces of geo. I use dynamic subdivision to keep the scene as light as possible. Once the pieces are complete, I will often add additional detail with Live Boolean. I have included a video demonstrating this process. It's fairly simple, but when there are so many pieces of geometry, it can begin to look very complex. Most of the geo is created directly in Zbrush, but I built some of the round parts in Fusion 360, and I used Marvelous Designer for the cloth pieces.
There are over 400 subtools, so organization is super important. Shout out to ExoSide, the team behind the ZSceneManager plugin.
If you're interested in a more detailed breakdown of what this process looks like, I have a tutorial on Plural Sight here: https://www.pluralsight.com/courses/modeling-rendering-a-face-mask-zbrush-keyshot-2121