After turning the sketch of the helmet part into a subtool I simplified the model with ZRemesher. According to the idea, the panel should have a similar protrusion with a profile as in the picture. The protrusions should not be smoothed, but have clear borders horizontally. How can I achieve similar at this stage. I would appreciate a video of something like this, or just some advice on what to use in such a case. 
Totally need shape like this but clear without all these unperfections happened due to manual drawing 
Start with Polygroup : Group by Normals to create polygroups on the visually distinct surfaces. Then ZRemesh with the Keep Polygroups option enabled. Search Michael Pavlovich YT channel for videos on how to use ZRemesher (or any other aspect of ZBrush).
thanks for response, will check this
Hi @MikeWasovsky228 ,
To add to what @tobor8man has said here, the core issue is that when you reduce point/polygons on a surface you will lose fine detail and detail like hard edges that were being defined by virtue of the density of the points on the surface rather than being topologically defined. This will also result in a coarser, less smoothed mesh.
In order to smooth the mesh again it will need to be subdivided. However, when subdividing up from a lower poly mesh and subdivision smoothing is enabled, edges will soften unless they are creased to protect them from smoothing, or reinforced by additional geometry along the edge.
Therefore, the topology must be drawn in a way so that the polygon edges fall exactly along the lines of the model that must remain hard edged. @tobor8man suggested a common way artists go about doing this in ZBrush.
Once you have accurate edge lines you can protect them from softening by:
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Use the creasing options in Geometry> Crease. Delete the creasing after one or two subdivisions and continue to subdivide for softer edges. This is much easier with well defined polygroups.
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Reinforce the edges with additional geometry. Two edges very close together are the same as a crease in terms of keeping an edge crisp when subdividing. However using geometry allows you to fine tune how sharp you want the edge to be as it will get softer the farther apart you move the edges.
