This isn't optimal, for training purposes. In the first place the biggest bang for the buck in terms of aerobic fitness gains happens in the high end of zone2 - counterintuitive, I know, but that's where you get the best balance between challenging your system and being able to keep going for a long time. In addition, fitness comes with training and recovery, not just with training alone. If you spend most of your time in zone 4 you'll just get fatigued, and eventually your performance will actually decline because your muscles aren't getting the opprtunity to recover and respond by overcompensating for your previous efforts. You can recover adequately from a Z2 ride overnight, but it might take two or three days for your system to adapt after going hard.

The old pros didn't have powermeters or even HR monitors, but experience taught them that they trained most effectively by putting in many hours of long steady (not slow) distance - LSD - and building in relatively brief periods of high intensity. Your best plan is to spend most of your time in Z2 and maybe 15% of your training time going very hard, doing intervals or whatever, with a rest/recoverybday scheduled after your interval session.

it may, at first. But the more time you spend there, the faster you'll find you are able to go at that HR.