Okay, since the film is called Zombi 2, it must be a sequel, right? Actually, the correct answer is no. It is a well-known fact that the italians not only like to rip off movie themes and general ideas, they are quite unashamed to release their own movies with titles that would suggest they are somehow related to earlier movies with similar titles. Zombi 2 is not an exception in this respect.
George Romero's famous zombie film Dawn of the Dead was released as Zombi in Italy. Following the success of that film, the zombie craze began in Europe and especially in Italy. Lucio Fulci, already a seasoned veteran at the time in 1979, was hired to direct a zombie flick to make money based on the success of Dawn of the Dead, and thus Zombi 2 was born.
Zombi 2 has almost nothing in common with Romero's film. There are obviously zombies in both movies, but even so, the zombies are quite different. In Zombi 2, the zombies move very slowly and look like they had been buried for a long time. This is a big contrast compared to Dawn of the Dead, where usually the only indication of "zombiehood" is the alteration in the colour of the skin.
Zombi 2 is a very famous cult classic, and for a good reason. It has nice cinematography and fantastic score by Fabio Frizzi. There are also several innovative scenes (e.g. a zombie fights against a shark under water) and some disgusting scenes too. The plot is dead simple and there is practically no character development, but that is exactly how it is supposed to be. In my opinion, a great zombie movie does not have to waste time building elaborate human relationships, it just needs to be entertaining. Zombi 2 delivers the goods.
However, Zombi 2 is a rather slow paced movie, and it is not packed full of action. Instead, the movie breathes nicely and is somewhat loose in its structure. Zombi 2 offers us many beautifully constructed and shot scenes that make the movie work extremely well. It is also great that Fulci takes the zombie theme completely seriously, just like in Paura Nella Citta Dei Morti Viventi, E Tu Vivrai Nel Terrore... L'Aldila and Quella Villa Accanto Al Cimitero. Zombi 2 does not contain intentional humour, but precisely because of that, it provides many good laughs to the viewer. Even though the film takes itself totally seriously, the viewer does not have to.
This is a very entertaining, fantastic Fulci movie that keeps growing on you during subsequent viewings. Highly recommended.