MI-4 -- Micro Intervals -- 40 x :15(:15) -- 20 minutes of repeating :15 sec. at VO2 max power (Zone 5) followed by :15 sec. of Tempo Zone 3. Note, the "off" portion of the interval is at Tempo Zone 3, NOT Recovery Zone 1.

If you are not hitting the prescribed power, in either the Zone 5 "on"
portion or the Zone 3 "off" portion, shut it down and live to fight
another day. This workout is all about quality and training with this
specific protocol.
This is an Endurance (Zone 2) ride with Micro Intervals. Also, add 15
minutes of Tempo (Zone 3) riding after the Micro Intervals to make up
the slightly longer ride duration, giving yourself at least 10 minutes
of Recovery (Zone 1) before you finish your training. If you find
yourself with extra time to train today, this would be a good
opportunity to add an additional 30-60 minutes of Endurance (Zone 2)
training, before tomorrow's well-earned rest day.