Interesting pairing question

[Firegriff]

So, in order to get a friend into EDH, I gave him a Yidris, Maelstrom Weilder to partner with his Zada, Hedron Grinder.  He asked what I thought an interesting question.  He asked if, after hitting with Yidris, if targeting Zada would cause all of the copied spells on every other creature to cascae as well.  I told him that I was fairly certain it would, making for an interestingly broken combo.  Was my conclusion correct?

[interfector]

Your conclusion isn't correct because Yidris reads  "as you cast spells from your hand this turn" but Zada copies the spell on the stack , so the copies are not casted.

Zada also doesn't work with "true" cascade spells like Demonic Dread because Cascade reads "When you cast this spell" and the Zada-spell are copied (and not casted) .

[Jabilac]

So, in order to get a friend into EDH, I gave him a Yidris, Maelstrom Weilder to partner with his Zada, Hedron Grinder.

Commanders need the Partner ability to actually have 2 commanders.  You could have an EDH deck with Yidris, Maelstrom Wielder as the commander or Zada, Hedron Grinder but not together.  Rules link

[Firegriff]

Yidris is the Commander, Zada one of the support cards.  Not partners.  When thecspell hits Zada, it has cascade as part of the spell already.  That's the reasoning behind my thinking that cascade would be copied.

[interfector]

Alright, I understand your reasoning, indeed the spell casted on Zada has cascade and is copied, but the cascade trigger only occur "When you cast this spell", and the copied spells are not casted.

[Firegriff]

"As you cast spells from your hand this turn, they gain cascade."  My thought was the spell gained cascade before hitting Zada, then became copied for every creature.  That was why I thought I would get clarification before a game was played and it came up.