I use power for my zones rather than heart rate, but in my experience you need to take these generic zones with a bolder of salt. Everyone is different and have different power and imagine heart rate profiles. For example the power suggested by the generic power range % for zone 6 (Coggan) would have me doing those intervals at 100W too low for me.

These percentages are just estimates for some generalized, generic rider... these are not necessarily the zones that YOU should use. Like I said the generic z6 level would have me doing those intervals 100W too low.. for me!
A much better way to figure out how hard to ride an interval is use the generic number.. then after a while you can gauge how hard you should be riding those intervals.

Another thing.. in my experience HR is usable for zone 4 pretty good for zone 3... great for zone 2 down.. but above zone 4 reacts too slowly to be usable...