I know people in the comments said this approximately three Ice Ages ago (given Internet time reckoning), but as nobody has turned this into an answer...
This sounds a great deal like Snow Crash by Neal Stephenson.
Matching points:
- "The protagonist is a delivery girl with a hoverboard"
One of the main characters is Y.T., a teenage delivery girl with a fancy high-tech skateboard. She meets the main protagonist - Hiro Protagonist - during a failed delivery run and the plot continues from there.
- "American neighborhoods are now walled corporate compounds."
One hundred percent straight from the book. The U.S. is carved up into myriad corporate fiefdoms exactly like this.
- "She gets into trouble and adopts an enormous Maori ally/love interest."
Not exactly. Raven is a seemingly-invincible Aleutian native and the main bad guy's henchman (more or less). He kidnaps Y.T. and there's clear evidence that she is -- despite her better judgement -- attracted to him. She's a reluctant companion to him, at best.
- "The villain is a Vietnam vet CEO and at the end, he faces off in hand-to-hand combat with the Maori."
Uncle Enzo -- the head of the Mafia corporate fiefdom to which Hiro (and Y.T.) are indebted, could be misremembered as a villain, but he's more or less a good guy. (As these things go...) He does indeed face off against Raven in hand-to-hand combat at the Los Angeles International Airport in the manner you describe.
Check out Snow Crash and see if any of that rings any bells!