Mega Man Zero Collection delayed in Japan

1. That's Zero.
2. Zero is way more manly than you can ever hope to be.

It is. . .

The DS?

I meant to put "handheld games".

coming to the Game Boy Advance in 2013

I've only played the first one, and from what I can remember, it was frustratingly difficult. Not impossible though. It's pretty much what you'd expect from the series in terms of difficultly.

It's a different type of "difficult". The whole gameplay is faster and you're movements are dynamic. It's alot like the X series if you ever played that. In the original Mega Man series the difficulty was your limited range of movement. For example, when you start a jump across a gap and some enemy robot popped out, you had nearly no chance to save your butt. In the Zero series, you can actually save yourself by reacting quickly, like changing jump direction in midair or destroy the enemy with your Z Saber before it reaches you. Also you can walljump and dash just like in the X Series.
If you're used to play fast paced games, you'll be able to beat the game(s) without spending too much time on studying level layouts or enemy patterns (which doesn't mean you won't die often). Although to get the best rank in all the levels you'll be required to know everything in advance. Specially the boss patterns.