Well, I just sold my Z7 for a TH 900 and I did own a D7000 for a year so I'll try my best. I listen to tons of EDM, DNB, and other electronica so what we listen for is likely similar. The Z7 is quite good, but it won't beat either the TH900 or D7000 at anything I feel. It will get you close, and don't get me wrong, the Z7 is very nice. Where things differ most with the Fostex for instance is that the Fostex is more extended in both extremes. I don't find the Fostex at all bright, but some seem to. In contrast for certain the Z7 is rolled off in the treble. It is a well done roll-off, reminds me of my HD650, but that memory is fuzzy as I sold that about 3 years ago now.
The Z7 does suffer a little from the rolled off sub bass, but it isn't anemic, but there can be no debate that it can't keep up with the Fostex or Denon. The other aspect of the Z7 that I had trouble identifying was what appeared to be a lack of depth or weight to things. Again, this isn't meant to read that it was poor in this regard, but to my ears there was a small lack of weight. For an analogy I use the idea of colour saturation. The TH 900 can by way of comparison be called more saturated than the Z7 would be. There were times that the bass was present, but it lacked a little weight and authority to it. I feel the mids are comparable with the Fostex again having a slight edge.
The Z7 is very strong in terms of the mid and upper bass going by memory. I think for musical genres that don't depend greatly on deep bass this emphasis is actually a good thing. If I had to give the Z7 a rating out of 10 for EDM, electronic music I would give it a solid 8 where the Fostex would score a 9, maybe a 9.5.
Now the Z7 is never fatiguing and the build quality and comfort is excellent. If a buyer was tight for cash I would say the Z7 would be the better value easily, but if budget can accommodate the Fostex the differences in my mind are worth it, but we aren't talking night and day. The Fostex is just a little more balanced sounding as well as having more authority to the sound (closer to reference, but still not reference). The D7000 would be quite similar, but it perhaps suffers from less instrument separation than the Fostex and it is less balanced sounding with treble that was a tad bright at times.
All of this said, for the $400-450 you can score a Z7 for that is pretty solid value there! Not sure if that helps.