The Good
As much of a pain as Damian can be, there is something in seeing him in action. Each Robin has had a different feel and with Damian being brought up to be a killer, he definitely stands in a different league.
The story begins a year and a half ago and then goes back further to see the life of Damian. We have a good idea what his life must have been like, growing up with Talia as a mother and being trained with the League of Assassins. There's a reason Damian is who he is and it's fully illustrated here why.
Tomasi and Gleason take advantage of the zero issue to show us scene after scene of Damian in action. Each year, he had a challenge to overcome on his birthday. It's great to see the glimpses and is almost hard to believe all this was going on in the DC Universe. When he was first introduced we heard about how he was raised. Now we get to see how everything happened.
The Bad
Even though it was great to see these moments in Damian's life, they didn't really give us anything new. We didn't really witness anything that we didn't already know as we have in the other Batman zero issues. Seeing Damian fighting sharks or man-bats is cool but again, it's just Damian growing up with Talia throwing challenges at him his entire life. I wouldn't want any new developments created or thrown in just to have a previously unknown fact about Damian but I just didn't feel I gained anything after reading, except for seeing Damian kicking some ass.
The Verdict
Damian is the little brat/sidekick you love to hate. As annoying as he can be, his charm is in the fact that he's a ten-year-old that can face Batman's enemies with no problem. He was raised by the League of Assassins and is the perfect little warrior. This zero issue serves to show us what his upbringing was like. We get to see the challenges he faced. It's great for fans of Damian to get to see these times but they also don't really add anything new to his character or the history that we already know. Tomasi and Gleason are deliver the goods as usual but because you already know what's going to happen and there weren't any surprises, it just feels like an extended visual telling of what we already know.