Hello everyone,
I would like a confirmation about the following game situation:

My opponent spent two resources and play: "Flames of Tzeentch" against my "Pistoliers" staying with zero resources in its pool; in response, I play "Iron Discipline" to protect “Pistoliers”, in response, he plays "Innovation" (four developments in his "Kingdom Zone").

Resolution:
Resolves: "Innovation", my opponent takes four resources.
Resolves: "Iron Discipline", my opponent spends the four resources just dealing with "Innovation" and cancels the protection of "Iron Discipline."
Resolves: "Flames of Tzeench", my "Pistoliers" take two damage and are destroyed.

To me it seems correct, can you confirm?

Interesting scenario. Yes, that is correct, and an example of one of the very few times where you can use Innovation to get resources and then use those resources during the resolution of the stack.

Technically he pays the extra 4 during resolution of his Flames, rather than during resolution of Iron Discipline, but that doesn't really matter in this case.

Thanks for your reply Entropy42.

In fact, it is one of the few cases where you can use the resources dealing with "Innovation" and use them during the resolution of the stack.