Ray had no buisness either yet he had it
Rayleigh is a different type of fighter to Zoro.
Rayleigh is like Roger and Shanks - all are swordsmen but they've gone down the internal destruction skill tree. They can hit without touching.
Zoro is like Oden, Mihawk and Ryuuma. All are swordsmen but they've gone down the excessive ryuo skill tree. They specialise in regulating the output (and subsequently strength) of their haki whereas the guys in the ID skill tree generally just have their haki either on or off. This path will lead to creating a black blade.
There is no character who has gone down both skill trees as of yet - these are distinct abilities, thus, it's highly unlikely that Zoro will ever learn internal destruction CoA. He has absolutely no need for it.