Whilst the point about running in Zone 2 is true, I thought it was proven that the overall difference was considered almost pointless unless Calories consumed was restricted too? (This was a long time ago, but I'm sure there was a whitepaper on it). For someone running at Zone 3 and eating normal food, the overall % of 'fat' calories burnt was usually lower, but overall calories burnt was higher, which meant the total 'fat' calories was about the same? I might be wrong, but I definitely remember reading something about it, but this could've been 10+ years ago.
But also, there's a million other reasons to run at Zone 2 anyway, not always, but definitely embrace it. Running at that Zone fixed so many problems for me, with injury, stamina, even just the desire to run.