I think you were going a bit harder than Z2 ride there. Z2 is usually defined as around 55-75% of FTP or 60-70% of max HR, so you're just over the higher end of that as an average.
Either way, the watts/HR is just a guide - the best thing to use is your perceived effort as your HR and watts can vary day by day to some extent. One of the key benefits of Z2 training is you can fit in larger volumes without getting particularly fatigued, so if you're going too hard and getting fatigued early it kind of misses the point.
Also, putting in harder efforts on hills during a "Z2 ride" will negate the benefits of Z2 training - you'll push your body into a different form of energy production and it will stay at this for ages even if you then reduce your power again, so as well as getting fatigued quicker, you're not actually getting the training benefits of Z2. Doing a mix of harder and easier efforts to get an average of Z2 watts isn't how it works - it should be constantly in Z2. If you want to do some harder efforts it's best to do them after your block of Z2 training, not before or during.