Its a shame most people have never heard of this game. ZOE2 is one of my more favorite games on the PS2 system.
ZOE2 is fast paced, non stop action, and fun throughout the whole game. Some boss battles can be frustrating, and others are way too easy. These are the only faults with ZOE2, along with the game taking 6 hours to beat. Despite these minors flaws, you will won't find many more solid games on the PS2.
It's hard to classifly what kind of game ZOE2 is. Some consider it a "mech" game, but the mechs in ZOE2 are more like the ones in the Gundam Wing anime series. Basically ZOE2 is a mech game that blends arcade flight simulator and hack n slash like Devil May Cry.
The weapons, the gameplay, the graphics, are excellent, thus making for an excellent game. All I can say is play ZOE2.