Okay, getting back to the topic. Purk, you have both, right? Could you please disable the 'sound enhancements' app on both the F & the Z and compare the output from the two?
If the output is the same, then maybe we could port the F's app to the Z and get the same sound signature :)
I don't use sound enhancement on my F & Z. The volume at the same at the identical loudness level. The sound signature is difference like I've been saying with the F is more on clarity while the Z is more energetic with warmer tone.
The Z should be the favorite among heavy metal fan given its sound signature. The warmer tone on the Z should work wonder with harsh metal recordings.