Honestly, I've never taken the Aculon apart. But I can try to list some points that I hope will be useful to you.
I guess the mushrooms are internal. In any case they die with the powerful UV rays. And in Brazil you should have plenty of them, leaving them in the direct midday sun, for multiple sessions.
Also test with 3% H2O2 (hydrogen peroxide) and then wash with distilled H2O.
Your binoculars are "modern", so there is a high chance that the fungus will die without a trace or damage to the coatings.
To clean and treat it better, it is preferable to disassemble the objective cell, reaching as far as the achromatic doublet. I don't know if the cell is glued or is stopped only by a screw or glued retaining ring (maybe, only that). You have to look carefully, because from the photos I don't see enough and I don't understand what materials they used.
Another alternative is to unscrew the entire lens tube from the prism body. I doubt Nikon used grains to lock it like they did for old good quality binoculars (but you first check under the rubber cover of the body). So, mark the position of the tube with the body (to go back to the same spot when you reassemble it) and then apply the right force to unscrew it.
It sees coming!
Once the tube is disassembled, you can try the H2O2 from inside. I doubt the fungus is between the two achromatic lenses.
Somehow you should succeed without big expense.
Edited by ECP M42, 22 June 2021 - 05:54 PM.