Yeah he’s using a difference zone terminology to what most people use and know as zone 2. Zone 2 in most people’s worlds is easy / low HR, but he’s talking about a zone related to his lactate threshold. I would typically call my lactate threshold pace as the comfortably hard kind of pace which I could hold for a hour. This would typically be a bit faster than my half marathon pace but slower than 10k. Including these runs are a main part of my Mara training. But I do one a week not 34566 that tits does.