I found some more information about Zero Mission, this time from
The Metroid Database:
Further information from various sources sheds a little more light on the mysterious Metroid Zero Mission and reveals that the game is, in all likelihood, not a prequel, but rather a beefed-up remake of the original Metroid. It looks as though we will be taken back to Zebes for Samus' first encounter with Mother Brain, but this time our girl will have all the abilities and weapons she's gained in all her adventures since then! Imagine exploring Metroid 1 with the ability to crouch, wall jump, speed boost and grab ledges, and taking on the game's enemies with the help of Super Missiles and who knows what other weapons! So far, it looks like while Samus herself looks much more streamlined than the big-helmeted sprite did in 1986, her animation pays a sincere homage to the original version, with Samus running notably fast and holding her gun arm out constantly.
Of course, the question remains, why the name Zero Mission? "Zero" usually denotes a prequel of some sort, so why not name the game "Metroid Advance" or "Metroid 2003" or something? This remains a mystery, as do whatever twists and additions Nintendo will throw at us (we already know there will be completely new areas, enemies and bosses added to the game). NCL's website does mention that MZM is a "tentative title," so it may change before the game's release (remember that Fusion was at one point actually titled simply Metroid IV). With an almost Hideo Kojima/Metal Gear Solid-esque level of ambiguity, Nintendo has tesed us with little other than screenshots, video, and a name. So, with no solid information available from Nintendo, all we can do is make a few guesses and wait for some more answers.
Hmm....as much as I'd like to see a totally new side-scrolling Metroid game, the idea of a remake of the 1986 classic does some enticing. It's new, but not all at the same time. With all the abilities of the four previous Metroid games (Prime technically isn't counted as the lineage), exploring Zebes for a second...I mean third time could be really interesting...
....I wonder if they'll work elements from Super Metroid into it....seeing how that game took place on Zebes and all...