I listened to the 4D recently. VEry good cartridge. The ZYX trademark sound but much more body and more dynamic. I compared it with a 47 Labs which had equal dynamics but a bit more warmth. The 47 labs also was a bit richer sounding. I then listened to a Dynavector XV-1s (all the same system but different arms) and the XV-1s sounded most natural. Most like music. I loved them all and would be happy with any. No one was clearly superior. My taste leaned to the ZYX or XV-1s but they sounded like opposites.
As for brass on top of the cartridge. I am using the Brass mounting plate on my SQ instead of the aluminum one. Much better dynamics. Basically it mimicks the description above from Stltrains of the nanomount. The ZYX can be extremely low compliance. Mass will naturally lead to greater extension of the highs and deeper bass. It will also bring you closer to the ideal resonant frequency outside of the the audio range.
As for brass on top of the cartridge. I am using the Brass mounting plate on my SQ instead of the aluminum one. Much better dynamics. Basically it mimicks the description above from Stltrains of the nanomount. The ZYX can be extremely low compliance. Mass will naturally lead to greater extension of the highs and deeper bass. It will also bring you closer to the ideal resonant frequency outside of the the audio range.