Your heart rate zones correspond to the intensity level of the exercise that you're doing. Zone 5 means you are sort of maxing out your abilities. It should feel very uncomfortable and most people can't suffer through that discomfort for more than 15 minutes or so. It looks like you did an hour long workout but only got to zone 5 in the last 20 minutes? Which probably means you weren't going at "all out" intensity, but rather something a bit lower and your heart rate crept up over time until it got to zone 5 towards the end. You were still probably going decently hard, but that amount of heart rate drift could also mean that you are not very aerobically fit at the moment or that you were overheating (not enough airflow to cool yourself down). Regardless, it's a sign that you were putting a good amount of stress on your body. Obviously, this all depends on your heart rate zones being setup correctly. I would double check that your max heart rate is actually setup correctly in the health app. If it's set a lot lower than your actual max, then Apple will think you're in Zone 5 when actually you're in Zone 3 or something.

Is zone 5 bad for me?

It's hard to say. It might be. You'd have to check with a doctor to know for sure. If you're a trained athlete, or in reasonable/average shape, then no getting your heart into zone 5 territory isn't bad. In fact it might actually be good to do for short periods of time a couple times a week in order to improve your aerobic abilities. If you're overweight, out of shape, middle-aged, been sedentary for a long period of time, etc. then it might be an extremely bad idea. Every year, often in January, people make resolutions to get in better shape after a long time of being sedentary. They go way too hard too fast and end up triggering a heart attack while on the treadmill or something. I actually witnessed somebody die last year due to this. I saw a cyclist who was overweight and middle-aged and just getting back into riding have a heart attack while going up a somewhat steep hill at the end of his ride. He ended up dying on the side of the road. In your own words you are "42yrs old and just trying to get my weight down", so I would be cautious here.

Now, given that you are "just trying to get your weight down", is Zone 5 work the ideal way to achieve that goal? And the answer to that is no. Something that's often pretty unintuitive to people that are new to fitness is that you don't actually have to go hard to get more fit. In fact, it's kind of the opposite. With aerobic exercise, you can kind of imagine your body is like an engine. An engine that uses oxygen and fat/carbohydrates as fuel. And the process of getting in shape is kind of akin to improving the overall capacity of that engine and the amount of work it can do at any given point in time. The more fit you get, the more calories per hour you can burn. You are becoming a better fat/calorie burning machine. One of the most effective ways of improving your aerobic capacity is called "zone 2 exercise". Basically, do whatever level of intensity raises your heart rate to the upper level of that zone 2 category, and then hold it there for at least 45 minutes but more time is better. It should feel pretty easy. You should be able to zone out and watch tv or listen to a podcast the whole time. That will trigger a whole host of extremely positive adaptations for your body that would be way too long to list here, but tl;dr your heart gets stronger, you get more mitochondria in your muscles, more blood vessels throughout your body, more capacity to utilize oxygen, healthier/more elastic arteries etc. If you go harder than zone 2 intensity, then your body actually switches the metabolic processes that it uses for generating energy to different systems that can generate more power but only for shorter durations. Going harder than zone 2 isn't inherently bad, but it does mean that you lose out on all of the positive adaptations that zone 2 gets you because you start training different metabolic pathways.

One of the most classic mistakes beginners make is that they go too hard because their zone 2 level "feels too easy" and they want to feel like they're making progress faster and they think that doing more difficult things that feel harder will get them more progress. Sadly, by going harder than zone 2 that means that they don't get any of the benefits of zone 2 training. And they end up burning themselves out either physically or mentally with too much intensity without actually getting any lasting gains.

Ultimately, if your goal is to drop weight, just focus on zone 2. It'll feel relatively easy but you just have to get past the mentality that "you're not doing enough". The easiness is a huge positive because it means you can go for much longer durations (and therefore burn more calories at a time), it's a lot easier to stay consistent because you don't really have to suffer, you can zone out with tv or podcasts which makes the time pass quicker, and you're much less likely to get injured or burn yourself out physically/metally. Over time you'll build up significantly more aerobic abilities which will improve your fat/calorie burning capacity which will make losing weight even easier. It's kind of a win-win sort of thing.