When you control doomdog octhros and activate this card. Special summon Dark Necrofear from your hand if your graveyard have 2 fiend type monsters at least or special summon Felgrand Dragon if you control Felgrand Dragon as destroyed monster by this card effect
This is how the IRL game works, but to simplify- Michizure is a little more picky on the last thing happening being the destruction. GHQ mills after the card is destroyed, though the wording is before the Problem Solving Card Text update.
Basically, warm worm doesn't care because it says If, but because Michizure says 'when', you can't use it here.
Warm worm destroyed by battle (mil 3), revived by regretful rebirth, at turn's end got destroyed by rebirth's effect (mill 3), which makes it revivable by Puzzle reborn, then assault on ghq (mill 5). That's one of the ideal combo