Welcome to the forum and I am sooooo sorry you are going through this very difficult situation with your bird! Now, before I say anything else, let me answer your question: Yes, it can be fixed - without a single doubt in my mind, I can guarantee you it can because I've done it [I have four zons right now but have had more in the past] and anything I do, anybody else can do, too. It's just a matter of understanding exactly what is going on.
I will go into the 'whys' of the behavior but, before I do that, I am a bit confused because you talk about getting the bird 'a few years back' but then say the bird is not sexually mature yet and this doesn't quite add up because zons are sexually mature by the time they are two years old so, if she [do you know for a fact, this is a 'she' because 'she' sounds like a 'he' to me] has been with you for 'a few years', the bird is sexually mature. Another thing you need to take into consideration when it comes to sexual maturity and hormone production is diet and light schedule. A bird that is free-fed pellets made with soy will mature earlier and will become overly hormonal easier - and, a bird that is kept at a human light schedule instead of a bird light schedule and free-fed protein food [pellets, seeds, nuts, nutriberries, avicakes, etc] will become overly hormonal in a few years, too. So, the first order of business is to make sure that the bird is getting the right diet [low protein, low fat, high moisture, high fiber, no soy, no animal protein at all] and the right light schedule [a strict solar one with full exposure to dawn and dusk].
The thing about keeping birds as pets is that they cannot adjust to a human lifestyle so we need to adjust our lifestyle to their needs [both physical and emotional]. Birds are photoperiodic which means that they 'mark' their life 'periods' [aka seasons, as breeding -spring and summer, molting -end of summer, resting -no sexual hormone production in the winter, etc] by the amount of light [photo from the greek word] they are exposed to AND what tells their body when the day starts and when it ends [the number of hours in between these two daily events being what tells them what season it is] is the different light spectrum that only happens during twilight [dawn and dusk]. Think of it as a stop watch, it starts running when the bird is exposed to the light of dawn and it stops when it's exposed to the light of dusk. When you expose a bird to artificial light before the sun is up in the sky and after it is halfway down to the horizon, you are artificially creating eternal breeding season. This added to a diet too rich in protein makes them overly hormonal. Because there is a huge difference between a bird that is normally hormonal [which happens every year during the natural breeding season of the species] and a bird that is overly hormonal which means that the poor thing has been producing sexual hormones way after it should have stopped. Birds have sexual organs that are only supposed to be active during breeding season and, as soon as the season ends, the organs stop producing hormones and go dormant, shrinking to teeny tiny BUT when a bird continues producing them, season after season, year after year, they end up with HUGE organs that end up displacing other internal organs creating best case scenario discomfort and worst case scenario chronic pain. This pain is worse for males than it is for females and it brings super aggression in male amazons [that's why I wonder if your bird is, indeed, a female].
Some species are worse than others and we have 'split' them into what we call hormonal species and non-hormonal species. Macaws are non-hormonal but all zons are hormonal and, within all the zon species, there are three that are worse and called the 'hot three' and the DYAs are one of the 'hot three'. BUT the problem is not the species or even the gender so much but the actual husbandry because I have three wild-caught females and one captive-bred male which was terribly aggressive when he first came because he was not only overly hormonal due to a bad diet and light schedule but also because he had been abused by his previous owner [he admitted to punching the bird] and he is now fine so, as you can see, it can be done.
This is what I would do:
1. make sure it's getting the right diet: you can NOT free-feed any protein food [it makes the bird very aggressive and it destroys its liver and kidneys], it needs to be a measured amount [mine get two level tablespoons of a cockatiel seed mix and three 'peanuts' [my birds think that all nuts are peanuts
but they would get, for example, - one almond, one half of a pecan and one pistachio], and it needs to get a lot of raw produce as well as cooked grains and veggies [mine get gloop and raw produce for breakfast and all day picking with the seed/nut mix for dinner]. Absolutely no animal protein, no meat, no eggs, no cheese, no nothing from an animal's body [they are herbivores, not omnivores as some people say].
2. make sure it's kept under a strict solar schedule with two hours of exposure to dawn and another two hours to dusk [this is essential and there is no way that you can reproduce dawn and dusk with artificial lights so you need to follow the sun].
3. I would NOT clip. It only makes things worse as time goes by because a] the only way a bird has of dissipating 'bad' [sex and stress] hormones is through flight [nature never counted on us, humans, thinking that we know better than her so she did not give them any other form of exercise] so, when you clip, all you are doing is concentrating the hormones instead of getting rid of them. b] a grounded bird is more prone to breeding behavior as the only time in the wild that they kind of like 'stay put' is when they are breeding. c] flight is a distraction and you want the bird to be as 'distracted' as possible [baths are good, too]. d] a bird that has been fully flighted will resent [and blame the humans] for the grounding, making things worse in terms of 'mood'.
4. I would not allow my child to handle an amazon. I don't allow anybody to handle mine - not even my husband [well, let me clarify this, my husband handles the parrot that chose him over me and can help cleaning, feeding, giving praise and treats, even putting them back in their cages when it's 'time' but this is done with a stick, never to his hand or shoulder]. The thing is that parrots are not and never will be family pets. It's not in their nature... they simply did not evolve this way. They can have a flock-mate relationship with everybody in the family but they belong to one person and one person only: their chosen human. And this chosen human is hardly ever a child for the simple reason that even adults have a heap of trouble learning a parrot's body language and understanding how different they are from, say, dogs - and children are hardly ever equanimous and even-tempered - an essential quality for all correct parrot handling.