I have seen a lot of tutorials online teaching how to create complex spaceships and mecha using boolean cutouts in ZBrush. Aside from the ZRemesh feature, which has questionable results on complex boolean cutouts (especially when you’ve piled a hundred cutouts onto one layer of armor) is it still standard that we have to take the boolean model into another application and painstakingly remodel it by hand? I feel like nobody mentions this when they’re excitedly teaching you how to punch all sorts of crazy shapes out of things. Obviously not as much of a problem when you’re going to a 3D print and don’t care as much about perfect topology, but for film and game dev this seems like a huge drawback.
Hello @sketchariffic,
Obviously intended output dictates the needs of your model. As you mention, working for print trades the need for exacting topology for other concerns. Working for animation, however, will require more deliberate, optimized topology. This is true of organic models destined for animation output, as well as hard surface. Even a character model will need to have its topology drawn a certain way for the most efficient results when animating. Most automatic retopology solutions will fall short of that.
There is no magic button that I’m aware of that will reduce a complex model to perfectly optimized hard surface topology of the sort a human could draw. It is a process, and sometimes there will be no substitute for manual re-topology. It is also a discipline, requiring you to know at what stage in the process certain types of work are appropriate.
ZBrush has many tools that can aid you, but there’s no single trick. It often requires a combination of tools–for instance using ZRemesher to get most of the way, then retopologizing certain areas by hand, aided by ZModeler with surface snapping and the topology brush. My advice is to try to use ZRemesher for what it is good at to save you a lot of work, and then do areas that require more precision by hand. Dont chase perfection with ZRemesher. If you try to ZRemesh a complex model with many fine detail areas all at once, your results often wont be great.
I recommend keeping the pieces of your model in smaller, less complex pieces. ZRemesher does a really good job of remeshing these with clearly defined edges if you use options like “Keep Groups” and “Keep Creases.” Polygroup management is critical in most high poly to low poly hard surface workflows. If you make sure that every edge that needs to stay crisp is bordered by separate polygroups, ZRemesher can usually clean these up pretty well with “Keep Groups” enabled. You can then instantly crease all the polygroups with the “CreasePG” option in the Crease menu.
If your model is composed of simpler hard surface shapes that have already been processed into clean, hard edged geometry of low resolution, with every creasing group its own defined polygroup, it will Live Boolean together much more cleanly into a more complex shape, and ZRemesher will then be able to do a better job with it. Some touch up work will always be necessary, making some skill with ZModeler fairly important.
I recommend taking a course or maybe a workshop on hard surface techniques in ZBrush. There are some great teachers out there. It is not a topic that can be covered in a forum post. It is a skill that can be developed, though, as evidenced by all the artists that do amazing hard surface work in ZBrush! 
Good luck!