Island, yes. Massacre, definitely. Zombies...not so much. Even if you haven't heard of it, the title sounds like something that you should have heard of. As a friend of mine put it, it has all the right words. The title, however, is misleading. Zombie Island Massacre, a Troma picture, is really more of a slasher flick, where the bad guys are "zombies." If you ever decide to watch this film, you'll see why I have that quoted. Having freshly come off watching Zombie 4: After Death, I was actually feeling pretty good about a movie that had a coherent plot and passable, if cheesy, acting, but that didn't save it from the slow pace and disappointing ending.
Several tourists at a Carribbean resort go on an excursion to the island of San Marie, to witness a live voodoo ritual. They do see what appears to be a corpse being reanimated, but it's never really made clear whether that was actually the case or whether it was a show being put on for the tourists. Upon returning to their tour bus, they find the driver gone and the bus disabled, and after their tour guide disappears also, they decide to seek refuge in a house they saw back along the path.
As they travel through the woods, something begins hunting them. Despite their best efforts, their number gradually decreases, usually by the couple. The movie does do at least one thing right, which is get rid of a lot of extraneous characters fairly early on by killing them off, although I which they had kept the stoner couple around for a little longer, for some comic relief.
The film will basically hold your interest if you have nothing better to do, although you will still be checking the timer on the DVD player to see how far into the movie you are. If you're a Troma fan, it may be worth taking a look, but don't expect a lot, even so.