a
It's the same as a Tora Gari because it has the Kanji '' Tora '', tiger and '' Gari '', hunt in it too.. As i said the name is different because he had to perform the attack while catching the sword in the air.. That's why it's named different..
In that panel if Zoro continue his motion, the 2 blades will be descending like you said from top to bottom in a vertical diagonal..