In attempting to emerge app-shells/zsh-4.1.1-r2 (currently masked on amd64), I discovered that sys-libs/libcap won't compile without -fPIC. Additionally, after successfully merging libcap, I had to rebuild both ncurses and libpcre with -fPIC for zsh to be able to link against them. After those changes, zsh emerged fine (and works perfectly).
ok, all fixed