I am having trouble playing these two sections because my muscles keep locking up and preventing me from playing it lightly as the arranger, Animenz, does. ()
Here are some general tips that I think could be useful for those specific passages.
First for the right hand part, don't hesitate to try different fingerings, and find the smoothest and "roundest" one for you, for example I my case, I would play it with this fingering to allow my hand to have a better rotating wrist motion, as well as to alternate fingers for the majority of the repeated notes:
Now that may or may not suit you, it sometimes depends on the pianist! Also, you could practise small sub-sections, stopping at key points of that rotation.
For the left hand passage, again broken sections can help, and you'll want to remove the weight and raise your wrist slightly after each base fifth. You could also occasionally remove one of the repeated notes to get the feel of it and watch the motion of your hand.
Needless to say that this piece is made for very advanced pianists. Don't hesitate to play it slower; playing this is already a great achievement anyway!
I'd have to see you play but playing those two sections myself, make sure you are using your pronator and supinator muscles so your forearm employs rotation. You don't need to play the thumb at all, your pronator will do it for you.
Don't ever press into the keybed. Let the weight and speed of descent of the arm play the notes. When using the arm properly, the fingers barely move.
Tension, fatigue and "locking up" occurs when we use two muscles simultaneously to move one bone. The muscles fight over which direction the bone goes and the tendons become stretched and strained - and our technique suffers. A second problem is pressing too hard. A third problem is using the same muscle twice in a row.
In piano playing, we have multiple movements such as up/down, in/out, forward/backward, gravity, pronation/supination and all these movements facilitate repeating notes without using the same muscle fiber twice in a row. Some people call it playing with grace but ultimately there are laws of physics going on which every pianist should know rather than merely imitating the grace of their teacher.
The problem with these "feel" or "vision" methods is they don't teach you the mechanics of the arm. These methods may serve many pianists very well but if there is a problem, they won't know how to correct it. Likewise, a pianist can have all the correct movements but they nor their teacher will see a hidden incorrect movement which are usually invisible to the eye. But, a teacher with a good ear can hear imbalances in the arm's alignment.
If your teacher can't suggest a simple adjustment which will give you these notes in an instant, either your teacher has no idea what they are doing on a bio-mechanical level or you've outgrown them and how far they can take you. It may be time for a new teacher.
Tension means you are doing something wrong and your teacher doesn't know what. More practice won't fix it. Proper practice will. It doesn't sound like your teacher can take you beyond that.
If your pool has a slow leak in it, you need to sleuth out the leak. Maybe even drain the pool to access it. Only knowledge and hard work will fix the problem. A bad teacher would say live with it, just re-fill it, buy a new pool.
Heed my warning, tension today will evolve into inflammation and scar tissue tomorrow. If you are lucky, you'll only have a mediocre technique and not develop syndromes and maladies.
If your car is out of alignment and it is eating up your tires, you can either keep driving, get new tires or, fix the alignment. If you have technical issues at the piano, you can either keep playing, look for magical exercises or, fix the alignment. Fixing the alignment is the answer to both.
What causes poor alignment? Your first teacher. If they allowed you to play with improper alignment, those first erroneous movements are hardwired into your brain and are there forever. It can be quite a challenge to eradicate them. Many can and have but, the next time you play a recital and are nervous, and you play from autopilot, those improper movements will come back with a vengeance and you won't be able to stop them. That is what most of those nervous mistakes are, improper movement creeping back in and taking over the proper movements. This in turn creates tension and locking up.
Any pianist who finds they have to shake their hands out is using two muscles at the same time. You can't beat it into submission. The laws of physics dictates that you have to fix it. Fight the piano and it will win. That's a guarantee.