If you ever wanted to know where the roots of Batman and other pulp superheroes and antiheroes lie, look no further than here. Zorro basically established all these important tropes: dual identity, masked crimefighter, a manservant, etc., that would pervade the latter adventures.
As for this series itself, I have a rather mixed impression. A collection of mostly loosely connected adventures with the titular character. The stories themselves are mostly brief, but some are over 20 pages long. Not particularly engaging or even slightly credulous, and often close to boring. At least the first half feels somewhat superior, and only because it utilizes the antagonist Captain Monastario, whose witty confrontational tactics really give him a well deserved status of Zorro's arch-nemesis in the pantheon of the latter's rogue gallery. Some comic relief in the hapless, bumbling character of Sergeant Garcia.
However, the plotting is secondary; the true star here is Alex Toth himself. He may have been a jerk in real life, but his work earns him the status of a legend. His drawings never lost their freshness; his style was unique, loose, yet always clean, inventive, and stellar. I won't waste too many words on his doodling achievement, but I don't need to. Get this book, open it, and let the art speak for itself.