my zone 4 is super easy, i meant 6 not 5 earlier as far as hammering, even my zone 5 isn't that exhausting for over long stretches, especially if I'm in a paceline.
Yup, your HRmax is clearly incorrect. Even looking at the website you went to it clearly states that Zone4 is race-pace, so by perceived exertion, you just aren't going hard enough to reach your true Zone4. Go redo your testing and HTFU on the test so the numbers really max out. Nobody on this planet can honestly say that zone 5 'isn't exhausting over long stretches'