This issue reprints DAREDEVIL #12 and #13, from 1966, two early appearances of Ka-Zar which establish his background and introduce his brother. Kirby did layouts for those issues, which John Romita, just recently returned to Marvel, finished. The most recent issue of THE JACK KIRBY COLLECTOR had some unused layout pages from #13, if you want to get an idea of what Kirby did. Interestingly, those pages are very different from the story as it was actually published, so I'm not sure if Kirby did two completely different sets of layouts or if what could be used from his for the original story were salvaged and adapted to the new story. There do seem to be varying amounts of Kirby in the finished product, for whatever reason, although I think we can safely credit much that's on this page to Kirby:
The story involved Matt Murdock taking a break from his law practice to go on a cruise, which is attacked by modern day pirates led by the Plunderer. As Daredevil, he allows himself to be taken by the pirates, and they go down to Ka-Zar's Savage Land, where we eventually, after battles with man-apes and killer plants, find out that the Plunderer is really the Lord Plunder (clever secret identiy, that), Ka-Zar is his long-lost brother Kevin, and they head off to England with Ka-Zar as a captive, ending on a cliff-hanger which leads into non-Kirby issues. It's all very confusing, and I have to say that I'm more interested by the story in those unused layouts, which seems to involve Plunder attempting to civilize Ka-Zar, and Foggy and Karen, thinking Matt is dead, flying to England having been hired by Plunder.
The cover is a heavily modified version of the Kirby/Romita* cover to DD #12, with some of the characters flipped, re-arranged and partly redrawn (most notably Ka-Zar's hair), and a big figure of Zabu added.
*see comments, apparently the cover is Kirby/Esposito, with maybe some work by Romita.**
**or maybe not.