A very quick listen to the KZ ZS7 using my favorite Spinfit tips agreed with @Torq’s impressions. Much better sorted treble, lots of bass. If I listen at really low volumes, the bass is about right, and thankfully clarity seems reasonably well preserved elsewhere. I also noticed the crackling on inserting both sides, but once in and sealed I didn’t notice it again until taking them out.
Here are some very quick and dirty measurements on my MiniDSP E.A.R.S. (diffuse field IEM compensation).
Measurements confirm that bass is very prominent, treble does seem more even than what I would see from my QT2 or the old KZ ZST, channel matching is not great (especially in the bass) and there’s probably a crossover at around 100 Hz which introduces an interesting wiggle in the frequency response. The crossover is visible in the excess group delay too.
That said, other than the crossover, the excess group delay looks very good okay compared to what I remember of my QT2 or Etymotic HF5., even at the extremes where things usually go off the rails a bit.
Gonna try a 20 Hz filter of -7 dB with Q 0.1 and see how I like that 
EDIT - Measurements were taken using the stock medium tips. Also, I realized that the group delay graph is zoomed to a stupid scale, which makes excess group delay look smaller than it actually is. Doesn’t actually look any better than the QT2.