The primary way is to start with a low poly mesh and project the details of your high poly model. Then subdivide and project again. Keep going until you have subdivided to a level where you’ve captured your detail. There are several projection methods but the newest and easiest is History Projection. Look it up on AskZbrush or Michael Pavlovich’s YT channel Project History
You can get you’re starting low poly mesh in a number of ways. For example ZRemesh and keep reducing until you have a nice quad, low poly model that captures the basic form. Or you could start with a simple quad model made from a primitive and ZModeller.
Note that maximum polycount for a single subtool is 100M polys and each successive subdivision increases polycount by four. So if you really want/need to max the polycount then think about the size of your starting mesh. 1500 polys will get you to 98M polys at subdiv level 9. But you should consider whether you actually need this many.