Corpse explosion

A shadowed streak flashes from your pointing finger to a zombie you have raised with the animate undead spell within range it then blossoms with a low roar into an explosion of necrotic energy. Each creature in a 10-foot radius must make a constitution saving throw. A target takes 1d6 necrotic damage per hit die of the target zombie on a failed save, or half as much damage on a successful one.
This energy spreads around corners.

When you cast this spell using a spell slot of 3th level of higher, you can target 1 additional zombie you have raised to explode and 1 additional zombie every 2 levels after that. (at 5th 3, 7th 4 and 9th 5.)