I have 2 show bred boys and they are very different to each other. In fact my situation is a bit like yours.
My older boy, William, was the perfect pup. Very easy going, very cuddly, confident but laid back, quick to learn, not destructive etc. He was my third Cocker, although my first puppy for many years and I know I was lucky with him as he was an easier puppy to raise than my previous two.
Then Louis came along and he was such a needy puppy and such hard work. I wasn't expecting him to be another William, but it was a real shock to find myself with a puppy that wouldn't settle at night until about 5 months old, seemed unable to focus on anything for even a second and gave William hell
Introducing a new puppy to an established dog isn't always easy. I made a conscious effort right from the start to give both dogs some individual time, so they would get a walk together in the morning (short enough for the puppy to cope with) then later in the day William would get a long walk on his own and Louis would get a short walk and some training on his own. Are you able to do anything like that with your 2? I also took Louis to puppy class once a week and William to his training class once a week. It helped Louis to socialise with other dogs and also to get used to being home alone when I was out with William.
Louis at 17 weeks was very much the same as Zach is right now, although less of a chewer. He was full of energy and I found him exhausting and had many moments of thinking that by getting him I'd made a big mistake. William spent a lot of time avoiding Louis and really didn't want to play with him, so I made sure that he was able to get away from Louis by either being allowed upstairs for a rest or by shutting Louis in his playpen with a Kong filled with nice things and frozen to make it last longer or a hide chew. Can you separate your 2 some of the time so that Kona can have some respite?
As Jane S has already said, I think a lot of your problems are down to how long Zach is in his crate. He's bound to be full of pent up energy after 3 hours in it twice a day plus all night. Is he more relaxed on days when you're not working?
I don't think there's anything wrong with his temperament. He's just a livelier puppy than Kona was and is at a very lively age.
Based on my experience with Louis, my suggestion is to make a real effort to spend some time with Zach on his own and do training and fun games to help him learn how to focus and to think for himself. Reward him when he gets things right and quietly praise and reward him when you see him relaxing. That should help you build up a bond with him and make your relationship stronger.
Try different fillings in Kongs and have a couple of them, so there's always one in reserve ready for action. You can use things like kibble, mashed banana, squeezy cheese, natural yogurt, peanut butter etc. Fill and freeze and try leaving him with one when he's in his crate in the daytime.
When you're there with him you could also try a hide chew when he's already used up some energy and you want him to wind down and relax. Chewing something appropriate can be a stress reliever so may help him a lot. I never leave mine to chew unsupervised and I'm careful about what chews I give.
Finally, what do you feed Zach? Some of the less expensive kibbles and wet foods contain a lot of colours, preservatives and additives that can make dogs hyper.
Please hang in there. Zach is at a very lively age and I really understand how frustrating that is, but if you put in the hard work now to help him you'll get there in the end. No 2 Cockers are exactly alike and maybe Zach will always be a bit more challenging than Kona, but he sounds like a perfectly normal puppy
