Both weapons are spiritual weapons.
The spiritual entities we know of is the death god or Dan when he uses reika.
I doubt you can break either of these two entities in their form.
Anyway the weapons go through a transformation stage.
The sword is liquid and comes out of a jar to form the blade.
The shield has a fiery state to it when material.
Both weapons are ethereal basically.
Now it is possible that in the state where the shield takes a material stage it can be broken, after all it deflected sasuke's sword, paper bombs and the hydra's head. However what is stopping the weapon to go into a state of it being spiritual again, therefore the attacks go through it, after all "it changes its properties in accordance with the attack".
If it was to stay in this material form and took a strong attack head on, lets say the 9 tails tbb and it shatters.
Going by its description, if itachi was to deactivate susano and activate it again, he will have these weapons so its not like shattering it, is the end of those weapons.
What i am not sure about, is that the weapons were said to deflect attacks meaning it would be hard to break it if has deflecting properties and we saw this with sasuke's sword, but also the snakes. [
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Anyway at first i didn;t want sasuke to have the weapons because in this manga nothing is unique anymore.
The ms was said to be unique, lol.
Rinnegan was said to appear considered a myth/mutation.
Mokuton was unique
Hiraishin was unique, until recently
So i wanted these weapons to stay unique to itachi, but now i want sasuke to have them.
Because we will be able to see ore of what the weapons can do. Yes some itachi fans hide behind its hype and DB entry, but at the same time it is underrated when you see people putting madara's gunbai above it or saying oodama rasengan gets past it, or people who still cannot wrap around their heads that, its altering of properties doesn't only govern elemental techniques.
So yh sasuke having it and it gaining feats should silence both who grip to the DB entry and claim itachi is invincible when such a thing doesn't exist, yes including Hashirama and does who underrated a weapon that has been labelled 'legendary' and compare it with other fodder weapons