Bob Kerrey's attack on the Thanh Phong village occured on Feb. 25, 1969. Thanh Phong in in the Mekong Delta. That is the same time Kerry and Zumwalt were in the Mekong Delta. So they were all there at the same time.
I am running into one problem with linking the quote to Kerrey in that so far I can only find it on partisan pinko websites, but I am still looking. It is funny that it is not part of Zumwalt's kid's quote on the Swift Boat Vets for Truth website. You would think LTCOL Zumwalt would mention that.