How to add a distortion/roughness on a Vector axis/mask? I have seperated Z-axis from vectors to mask a texture to appear only on faces (normals) facing upwards. This is working this far.

But the masking is linear and "clean". Is there a method to distort this vector "mask"? so that there is some "rough edging" or changes along the Z axis along the mask.

I hope my question makes sense. Thank you for advance.
Building off of my answer here I add in a Noise Texture which creates the distortion.


The three selected nodes are the new ones for the distortion.

From left to right in the image below. The Z component of the normals, the Noise Texture, and the two multiplied together to make the final mask.