How does the armor protection against the attacks of the elements work?

The question is as follows. If I have 75% protection from the elements and in addition I have 70% protection from the elements due to armor, will these indicators add up? Or is 75% already the limit, and in this case protection due to armor will not do anything?

Damage reduction from armour is applied to the damage first and then elemental resistances are applied to the remaining damage.

From your example of 70% armour and 75% resistances when taking 1000 fire damage you would take 75 damage.

In practice it's not that simple since the scaling of damage reduction from armour depends on the magnitude of the hit.

I have 90% reduction from armour and 75% resists and around 300 regen.
Normal mobs damage is so light that I don't even see my life meter move.
Magic mobs only do noticeable damage when I stand in telegraphed aoe attacks but can't kill me.
Elemental rares take chunks out of my hp with big attacks but the attacks are so slow that I recover the damage between them.
Xesht doesn't do elemental damage and one shots me at the highest difficulty with the big attacks

Thank you, I see. Based on your answer, it turns out that protection from natural damage due to armor makes sense, even with 75% resistance to the elements.