>= x11-drivers/ati-drivers-12.8: need app-arch/unzip. Version 12.6_beta_pre897 too, if I am reading this correctly (otherwise it's 12.6). When I made a new install from stage 3, I found that ati-drivers does need app-arch/unzip, but does not DEPEND on it. Since it hadn't yet been installed on my system, I needed to do so manually first. I wanted so save the log, but forgot. Anyway, "grep zip /usr/portage/x11-drivers/ati-drivers/ati-drivers-12.*" shows this quite clearly. Please add app-arch/unzip to DEPEND. Thanks for your work!
*** Bug 443544 has been marked as a duplicate of this bug. ***
Fixed in x11 overlay, thanks for pointing this out.
Fixed in 12.11_beta11 in portage.