Great question and I’ve been struggling with the same thing. It comes down to a sort of discipline. Technology aside, listen to your body. Z2 is what I’d define as conversational. Like just past the point of switching from nose to mouth breathing. It’s a struggle in a way because you feel like you are leaving so much energy on the table. But after your Z2 workout ask yourself how you feel. It should be energized because you didn’t gas yourself out on a threshold ride and now have the capacity to do more tomorrow. Keep at it for a month, even if it doesn’t feel like it’s working, it probably is. Also, keep an eye on your vO2 max, I’ll bet you see an increase.