You can, for example, Summon 1 Zombie from your opponent’s GY, and 2 from yours, etc.
This effect targets 1 or more monsters in the GY(s).
After the Zombie(s) are Summoned, they are no longer targeted by "Doomkaiser Dragon/Assault Mode".
Even if "Doomkaiser Dragon/Assault Mode" is removed from the field, those Zombies’ effects are still negated, and they are still destroyed during the End Phase.
After the Zombie(s) are Summoned, they are no longer targeted by "Doomkaiser Dragon/Assault Mode". Even if "Doomkaiser Dragon/Assault Mode" is removed from the field, those Zombies' effects are still negated, and they are still destroyed during the End Phase.
Destroying the Special Summoned monsters in the End Phase does not start a chain.