Good to hear man! I also sold my first 4z to tour around with other headphones but I always missed their delicate signature and had to go back. I thi k what makes them work so well with EQ is the combination of having extremely low distortion and while I dont know exactly why, from my experience planar drivers have the ability to take what the eq is telling it to do and exaggerate whatever frequency range you want it to without disturbing adjacent frequency ranges. I think the difference is the physical excursion of voice coils bouncing back and forth doesnt allow it to have as much control as the magnets pushing the films in planars (again these are my personal conclusions that could be completely wrong, but make a but of sense to me)
As far as how my FR looks right now, I am using this graph from oratory on my 4zs.

it is nnormally intended for the lcd 4 but to me it sounds amazing. When I first got the 4z, all I did at first was give it a 3db high shelf for bass in addition to the audeze reveal lcd 4z eq preset in roon. This gave it the boost I needed for electronic music while the boost in the 3 and 9k range gave the highs a bit more life although not much.
After selling my 4zs and moving to utopia, I found I enjoyed the brightness a lot but eventually it did get fatiguing for me for a while. So once I got back to the 4z I looked around for eq guides and even some professional eq for certain things I wanted to hear to see if I could apply them to my custom 4z curve. What I wanted was high bass, and sparkle in hats and cymbals, more noticable transient in snares, and a bit more grit to vocals and synths (I listen to mostly bass heavy electronic music as well as indie/ funk) after playing around for a while I felt I was completely changing the detail of the 4z while painting its signature. Bass had a new rumble to it, vocals where smooth but crisp around vowel sounds, synths had more grit, snares had more sparkle, but I was still missing a sort of cohesiveness to the sound. That's when I came across oratory eq for the lcd 4. His goal was to shape the sound towards the Harman target, which coincidentally, was exactly the sound I was looking for when I was searching for eq. I followed his custom eq curves in roon and wow the sound is just amazing. Super immersive, full of detail, bass has oomph and it completely transformed the headphone for me.
I would highly suggest using his eq curve and then taking a good afternoon to play around with the peaks and valleys to tune it to the music you enjoy most. For me i lowered the dip around 1k about .5 db more, set the high shelf more so around 125, boosted the 10k and up range about 1.5db for more air
I know it seems extreme. But trust me the 4k can take it. It's obviously far from neutral but it's fun so why not