neither of you understands what he wants to do.
they got a 7/8 heroic instance ID, lets call that ID A. Chances are they won't kill madness today (mostly because tabs is a baddie) and want to extent it so they don't have to 'waste' time on their 2nd spine kill and can instead progress on madness.
So today after wiping some on madness, the instance is set to normal and they kill the encounter (without zoyt's druid in the raid, but that shouldn't even matter).
As that is a normal kill, ID A should still be 7/8 heroic as the normal madness kill shouldn't get saved as it's normal, right?
So on Wendesday everything resets and they clear 7/8 DS normal (for trinkets, set items I guess?), but no one gets locked to an ID here as everything is done on normal. Then Zoyt logs his druid and extents the 7/8 heroic from ID A and everyone joins that raid ID.
From how I understand it, that should work just fine. Afaik the madness kill in the current weeks reset should not get locked to ID A as it's on normal. Never tried that though, so no guarantees.