Zolo is more of a failed copy of any samurai based character from rurouni kenshin and guta from berserk. Lol. Nothing is interesting of that character. Just there for fan service panels. He is hardly a character except for some moments in wano.
zoro is a very stock archetype character but hes written very well for being that simple imo. the buddhist background actually comes across in almost everything he does and says, which is impressive to me. hes a very basic samurai character who serves his boss and has simple goals but the whole "asura" thing is actually really well researched and oda is always trying to represent that in how he acts.
zoro is a character who accepts pain and suffering so that his leader doesnt have to, whether its symbolically or just actual literally like in thriller bark, and hes the one willing to do things that arent noble, but still toward noble goals. hes going to drink, and murder people, and be lazy, and talk shit, but he's serving luffy who is like a buddha figure himself so he enjoys the fruits of wholesome karma while being entirely unwholesome himself, blah blah. its fun that theres a little more depth if you dig for it