I have a few comments to Diana's excellent essay. Diana describes Nietzsche's lambs and birds of prey analogy with horrifying details and many potential ramifications. This must lead to a skewed result.
Masters are always masters and only masters, slaves are always slaves and only slaves.
Z is a book about, primarily, individual development. Yet one must embrace and fight through this stage. The lion is the next stage, a rebel who says no and refuse to be chained any more, and more, the lion is a rebel who must appropriate and build in itself the kind of power that it is fighting against externally, in order to create the conditions for a free and self-directed self that can become a Free Spirit or creator. According to Nietzsche, slaves aspire to liberty and masters aspire to nobility. The lion aspires to liberty, and thus can be said to be a slave.