Looking at your HR data below, periods of 90 mins in Zone 4 are not out of the question. But a lot depends on how you feel at that pace. If it’s comfortable and you could go on, then it’s probably Tempo.
I trained using HR up to this year. HR zones are just theoretical/ statistical abstractions. But you have loads of good HR data, plus the experience of knowing how it feels to ride that way.
I would say forget the formulas and develop your zones to be meaningful to you. With stop/ starts, hills/ flats, winds/ draft, not to mention cardiac drift - I think the actual bpm is less important than how you feel, and how you know a given HR is going to impact you.
Besides lactate threshold, I think the other important marker is your 2-4 hour pace. Call that the top end of Tempo. Then the range between them is steady state/ sweet spot (SS). LT is, say, equivalent to FTP (your notional 1-hour pace), so SS is hard but do-able. Experience lets you relate the do-ability to HR - at 170 I can last x mins, but if i drop to 168 it’s x+n.
If you do this you can customise the zones to meaningful things in your cycling.