The plot line in ZombieLand is almost non-existent. We're technically following Columbus, who meets up with Tallahassee and they ride together for what is only to be to a certain place. They hit a snag in these plans with Wichita and Little Rock, but then all four of them eventually team up. Here's where the plot suddenly falls away. Columbus, as his name implies, is attempting to get to Columbus. Wichita shoves her foot in her mouth after having referred to it as a barren wasteland of zombies. So, Columbus, without really much reason other than a vague love-interest that shouldn't really exist already beyond superficiality, stays with the group. As they continue the travel, they group grows fond of each other enough to agree to stick around until Pacific Playland, the destination of the two women. Before this they travel into Beverly Hills and stay at a famous person's house (I won't spoil this as they even star in the movie), where they make base for a time being. After an almost kiss between Columbus and Wichita (predictable, but it wouldn't have been so bad if the love story wasn't so necessary to keep Columbus along but forced in the sense that there was no reason for these characters to suddenly want each other--yes I know they probably haven't met much anybody else and it's probably out of necessity but the dialogue is so lacking here we don't even see the progression), Wichita and Little Rock suddenly "flee" because of their "trust issues" while the audience politely ignores how stupid this sounds. Columbus decides to chase after them, while Tallahassee is logical character with a logical development and doesn't care. Columbus does have, admittedly, a good line here which seems to give Tallahassee a reason to come along. They drive off to Pacific Playland where the two girls have successfully alerted every zombie in the area to their presence, drove the car into the water for some reason, and our now stranded on a ride that gives them the height advantage. So the men set out to save the damsels in distress. Tallahassee, still maintaining his simple but believable character, goes on a killing spree, here, in all fashions, humorous and tactful, while Columbus awkwardly makes his way to the girls. During this he so self-skull-stabbingly has to run into a "Haunted House" which again the audience politely ignores. Finally he makes his way to the women but has to have a final showdown with a dreaded enemy, which is both funny and awesome, and Columbus has to step up from his cowardly, rule-maker self and do what's necessary. (Of course, the nerd can never just be a nerd, he has to be a nerd that then goes through a change which makes him a MAN.) They save the day and Tallahasse finds a twinkie, successfully fulfilling character arcs for the men and sort of for the women, as they clearly won't have "trust issues" again at least with these two guys. At the end they all remain together driving off into the sunset.
As plot lines go, ZombieLand is truly a comedy in almost all senses, especially in its inability to really create any form of rising action. Like many lazy plots, it moseys along with cheap thrills, humorous antidotes, and finally shoves a forced action sequence (or dramatic one in other movies) at the end to make you feel the movie was building to something, going somewhere, and the audience feels satisfied. The problem here, however, is the final action sequence is somewhat empty because there was no rise to this point. The only real intrigue is within Columbus, because he is the only character with a real arc beyond superficiality. Even so, we don't see him struggle with this possible change more than one or two nonchalant times. It isn't a focus of the film. As such, our final action sequence is empty beyond sensationalism: motivating music, humorous antidotes, people shooting things, and the final showdown for Columbus with a sort of innocuous reference to the beginning as if this shows us "coming full circle," when really it's just a coincidence and we really didn't need to know about it in the beginning, anyway.