Say I place ZRemesher guides on a high poly model, and ZRemesh, and it looks pretty good, but you feel maybe one more ZRemesh using the same guides at this low level would really nail the result, is it possible to copy the guides you originally used and paste them again?
I’m finding 2020’s ZRemesher absolutely amazing.
I’m not aware of a way to do this off the top of my head. There may be a scripting solution if you wanted to check over in Scripting Help, but that is not my area of expertise. There are a lot of weird things you can do with curves, though, and perhaps someone will come along and dunk on me here for your benefit. 
However, in my experience the question is usually the sign of someone who wants a little more from Zremesher guides than they are intended to provide. Counter-intuitively, the Zremesher guides become less effective the more of them there are, so if you’re finding that your guides are not something you can quickly and easily re-draw, you may not be using them efficiently. They are meant to be general suggestions for flow, not a roadmap.
They were one of the earliest tools ZRemesher had for directing polyflow, but in my opinion they are completely replaced by more recent additions. The “keep groups” and “Keep Creases” options in Zremesher, allow you to use polygroups, and creased edges to influence edge flow. Some of the benefits offered by this:
Polygroups and Creased Edges can survive the Zremeshing process for multiple Zremeshes.
Both of these features are useful for hard surface as well as organic mesh polyflow.
They are supported by more features, and will allow you to work back and forth between them for many interesting strategies. For instance the Stroke> curve functions > Frame mesh provides a lot of useful options for quickly generating curves with polygroups, and the Crease menu can generate creases around polygroup borders instantly. Once you get comfortable with the fact that in Zbrush polygroups, polypaint, and masking are all pretty much interchangeable, you can do interesting things like use polypaint to paint your guides.
Opinion: Try not to chase perfection too much with ZRemesher–it’s a bit of a trial and error trap. An auto-retopology solution is designed for situations where you only need topology that is “good enough”, and will not replace a human’s ability to draw hyper-optimized topology for situations where that is required, like production quality animation, or some hard surface work. If you need that, you will have to retopologize manually in any event. If you don’t need that, in my opinion it is preferable to just get in the ballpark with Zremesher and manually correct small imperfections some other way, like Zmodeler, rather than trying to chase that last 5% with ZRemsher. Your experience may differ.
Sorry for the late reply. Thank you for the complete reply Spyndel, you described the situation, the experience, and outcomes very well.
Yeah, my mesh is simple, but it twists in a spiral, it’s only needs a couple guides, but they are really long, but what you said about chasing perfection is very very true. And I like what you said about using more guides tends to make the outcome worse, very true.
I hadn’t thought about groups and creases, I can’t crease, but it would be amazing if I can get polygroups working on it, that would solve it.
It’s amazing how close ZRemesher actually gets. Just a single edgeloop sliding out of place here or there is the only problem. I feel I could actually nail it if I got the magic number with polycount. If it’s too low, the loop slides right, too high, left as an example. Anyways, your reply was awesome. I think you are 1000% right. I may try to crease the remesh, and use groups to force an edge that I can crease… something like that. Should work out perfect.
This is why–again, only my opinion–I recommend becoming familiar with ZModeler. Even if you aren’t going to be doing any modeling with it, it still has very useful tools to supplement ZRemesher and make those minor modifications, rather than continuing to pursue diminishing returns with ZRemesher. It can quickly add or delete loops, fuse points together with Point > Stitch, spin edges, and the always useful point and edge sliding.
You can also always rip out a piece of topology anywhere on your model and re-draw it with the topology brush, so it isn’t necessary for Zremesher to do all the work. But it can free you the labor of doing all the non-critical areas, allowing you to focus on areas that need special attention.
You’ll discover this on your own, but if you can polygroup, you can crease. Crease tags are temporary, and can be removed once they no longer serve a use. You can even use the Crease Curve brush to cut creases into your geometry (it’s going to be remeshed anyway). With the “keep creases” option, these crease loops would function like guides, and would be a quick and dirty way of creating guides that would survive the Zremesh process.
When using Zremesher to simplify models, the current Zremesher workflow I use is all about polygroup management (especially important for hard surface work), and I use ZModeler to help tweak the meshes as I reduce them in stages. I just use Zremesher for what it is good at, and other tools for what they are good at. Experimentation can be fun, but excessive trial and error is a serious threat to the enthusiasm for a project.
Spyndel, you are the man and a wellspring of information. I guess I haven’t been using ZBrush as often as I should, because all of these suggestions are very reasonable. I didn’t know about the Crease Curve brush at all, and I appreciate the topology brush link, I’m using that a lot, but not the right way, I literally needed a link to show me how to not backtrack so much. I also will take another look at Zmodeller, some of the advanced functions, I need to take a closer look at. If I had more time, I could literally hand topologize my whole mesh rather quickly.
I appreciate you helping me with these issues. You describe ZBrush in a way that I enjoy and really help.