Remember Zwift power HR zones etc are guides. Use them intelligently. Their based on averages and may not reflect your personal weight, height, power, body shape or fitness. They are at best ‘approximate’.
I use Zwift and Ive dumped HR zones for power. It was over complicating getting fit. Power is way more accurate and, as you have seen, you can see the increases your training brings as your FTP increases. Something I couldn’t do with HR year on year.
Ride on!