I don't really understand why people are complaining about how short this fight was.
Zoro and Pica first started fighting in chapter 740, where we had a full page of Zoro dueling Pica in the palace and wondering how to actually injure him. However, this fight ended just before we returned to that scene in 743, so we saw Zoro wondering where Pica disappeared to. Pica attacked again in 748, but the fight between them didn't resume until 749, where we got about another page of the two of them clashing blades and facing off. In 752, we got another third of a page of them fighting with swords, and in 752, 2 full pages of them swordfighting, before Pica reverted to attacking Zoro using stone (another two-thirds of a page), finished up with another 2 and a third pages of Pica attacking Zoro et al, and Zoro hitting Pica with 1080 pound cannon and talking smack. 755 has them talking more, and another third of a page of them fighting. 769 has a few panels of a double-page spread devoted to their fight (more swords). 770 has two and a third pages of them fighting, before Pica switches to fighting from the plateau with charlestone, which results in another two pages of fighting/exchanging quips, along with a few more panels scattered throughout of Pica's attacks and Zoro dodging. 771 gives us another page of their fight, then 777 gives us 2 and a half pages before Pica goes off to destroy king Riku, which leads to a page of Zoro's reaction, then 3 pages of Zoro planning a response. Finally, we had 13 pages directly of their fight this chapter, with several more of things closely related to their fight.
In terms of content, that's 31 full pages of their fight (30 in the final showdown; I think that makes it his second-longest fight to date in terms of pages), and Zoro used 2 named attacks and innumerable unnamed ones (although Zoro's 2 named attacks inflicted the only injuries either combatant received), while Pica used 3 different named attacks and innumerable unnamed ones.
In terms of in-story narrative, Zoro was portrayed as a match for Pica from the start; even inside the Palace (where Zoro was surrounded by stone) Pica wasn't landing blows. However, Zoro also wasn't able to injure Pica, so they had something of a stalemate going on. However, despite this, Pica was reshaping the island significantly and causing all kinds of mayhem for others while Zoro fought him. While people expected this to return to the old "Zoro loses more blood than is contained in the human body" challenge formula, the challenge in this fight was more a challenge of Zoro's mind: figuring out how to bypass Pica's defenses and injure him, to prevent him from doing more damage to others - others who can neither effectively defend themselves, nor take blows as well as Zoro can. Not that it wasn't also physically strenuous, it's just Zoro was clearly up to that part from the start.
And in terms of the duration of the fight, Elizabello used his king punch (light version) against Pica's arm just before Zoro's second showdown with Pica began in 749, and in 772 Elizabello says his king punch is ready again. That means Zoro and Pica were fighting for a minimum of nearly an hour; I'd call that pretty respectable. In fact, based on the timing between the king punches, it seems like the fights with the officers all lasted a minimum of about half an hour, and quite possibly nearly an hour. Yeah, we didn't see everything that happened in the fights, but there was so much going on that I think it was kind of inevitable that a lot would be off-screened: it's better that Oda didn't get bogged down in showing us every detail of every scene, or we'd be here another 5 years and have forgotten about all the rest of the story by the time Dressrosa ended.