Pica was how big?
Maybe small Mountain Size at the very Best?
The Cube (name of the floating cube thing not very original), is what CSK slashes and this thing is pretty much the size of a small island, or at the very least the size of a mountain.
and that last slash attack of the CSK in the 4th scan, actually cuts an area way bigger Cube.
see the tentacles next to the slash, that is Cube's massive tentacles, and the attack goes off panel too, which is the best part.
I don't think Zoro's slashes are better than CSK tbh honest with you. The CSK is like Madara's PS level.
Zoro is impressive, but I think he is a sightly below someone like the CSK.
It's fairly easy to see that the slashes are comparable in power. While that cube is decent size, Erza was able to break through the bottom rather easily while fighting a demon, which tells me it wasn't that big. CSK is also slow, which would be his downfall against someone like Zoro.
Not to mention we haven't even seen Asura. Prolly won't see it til Wano, but I'm excited nonetheless :P
Also, apparently Zoro's 1080 pound cannon continued off panel as well, since it cut Pica entirely in half instead of just down to the mid section.