Here's a mountain century I did where I finished in the top 25 out of 1000. Your HR stats are freakishly similar:
http://app.strava.com/rides/9040501
Z1 - Endurance 0-118 0:22 0%
Z2 - Moderate 118-156 1:40:02 31%
Z3 - Tempo 156-175 3:08:08 58%
Z4 - Threshold 175-194 37:47 12%
Z5 - Anaerobic 194+ 0:00 0%
These are hard rides, but do-able. I actually should have had a significantly higher portion of time in the z3/z4 range, but cracked hard on the climbs, and climbed in upper z2/low z3.