1) When in doubt add more aerobic base training volume. In your case that sounds like it needs to be in Z1. It does not matter what days this occurs.
2) There is plenty of Z3-4 training in the plan after the ME block. We use the ME block as a preparation for the more conventional high intensity interval training. You get more from those Z4 intervals if you have more fatigue resistance legs. Doing Z4 during the ME block runs a big risk of overtraining. Z4 has a powerful ME training effect so you’d be placing a big ME load on each week. You may be able to do that depending on your work capacity but I’d be careful and add that in very slowly to see hoe you respond.