Your normal maps are very hard to see in your attached images, but it looks like there is some pixel smearing going on. Zbrush does not like it when UVs are exactly along the 0 or 1 UV axes, resulting in a similar bake. If you have UVs resting on these axes, try scaling them down just slightly so they rest inside the 0-1…
The blue lines are UV 0, the major black lines are shown for every whole UV unit (UV 1, 2, etc.). Your UVs are not touching nor overlapping the 0-1 UV edges, which is good. But you have a lot of wasted UV space. You should pack all these into the lower-left quadrant, the square from U0/V0 to U1/V1. Try to keep the spacing…