Before diving into your workout take the time to read the structured workout. Zwift won't convey the nuance. Make the workouts your own.

Analyse the details of your 85% workout to get a sense of how well you did and whether to progress it.

Using Training Peaks we can go in and look at the metrics - power, heart rate and cadence - to check if you did a good job on your workout

Three metrics define how to do a workout: power, heart rate and cadence. Take a closer look at your workouts in Training Peaks.

Editing the structured workout is easy.

Why are different rides with the same average power leaving your legs feeling so different? Pacing. Keep an eye on your variability index.

You might not think so but if you are riding at threshold it is like racing.

Some times you need to create a lap manually so you can look at a specific part of your ride data.