Topology.... The Horror!!!

Topology is the hardest part to learn of ZBrush, it's main focus is the surface and optimisation areas in a 3D object. These will determine whether it's a high-quality model, having said that, you will only optimise a model when:

Before you start: (The Base Mesh is Level 0)

As things change: (While you sculpt with Dynamesh)

When you're done: (animation ready or game-engine efficient).

The annoying thing with Topology is that it uses Tessellation (M.C. Esher), like puzzles. It's all direction and flow.

(M.C. Esher tessellation)

The problem with ZBrush and topology is the Dynamesh tool. This feature doesn't give the topology any direction or flow, it keeps organisation in the incorrect and inefficient manner where they become steps.

It does have a solution to this problem, ZRemesher. A feature that is very helpful for modellers as it can decimate the poly count in a sculpt while keeping it's form. You choose how many polys you want it to become using the Target Polygons slider, you choose 1 and it will reduce the model to 1000.  They are other option sliders, but you can lose detail in the process. Using ZRemesher and the PolyPaint tool, you are able to select areas where you want to have a higher concentration of polys.  Another way of raising the topology is by using the Project Tool. You are able to raise the volume of older models to duplicate the original sculpt, remember that the Distance slider needs to be adjusted depended on the model.  Remember that there are many ways of reducing the poly count and increase topology efficiency in ZBrush.

(Topologised Mermaid)