As I said in my first review, it is a fighting anime featuring a contest for Holy Grail between 7 pairs of Masters and Servants. It includes magic associations and mages, Church, legendary and real heroes (Gilgamesh, Alexander the Great, "King Arthur"), mercenaries with guns, and many other elements. The premise is simple, but plot is complex (for an anime) and fast, full of convoluted plans, and it is interesting to follow.
This second part of "Fate/Zero" anime is much more intense than the first one, and it actually contains some real fights between Servants - all fights in first part ended in draw or were interrupted. I already said that it is much faster than first, and it is also much more violent and crueler. I was surprised several times with what happened to characters, especially with Emiya Kiritsugu in his recollections. Characters are the same and there are no new additions, but we learn more about history of few of them. I was very pleased and surprised with the ending - also, I found the scene with nude Gilgamesh quite hilarious.
This part finally explains the connection between "Fate/Zero" and "Fate/Stay Night", but you can learn even more from Wikipedia article. I also caught some references to "Kara no Kyoukai".
Anime retains high visual and audio standards set by first part and are really good. I was impressed how CGI was inoffensive (I usually hate when they use CGI of generate large number of doll-like soldiers...).
All in all, everything good I said about first part, stays good in second or gets even better. "Fate/Zero" (both parts) is one of best fighting anime I watched, a superb dark fantasy set in contemporary setting and combined with much violence and action, all packed in impressive animation - as its over-9.00 AniDB rating proves.