Keep on looking for fan sites. (Genning up doorway fan sites, however, is frowned upon.)
I've got a short list of lyrics writers, some much more important by any measure than Zach, that don't [yet!] have a category. It isn't for lack of me looking: the sites just aren't there.
Yet. Sometimes an editor will get interested in a person for which one site has been submitted, and go look for enough sites to build a category. (The ODP averages over 100 new categories a day.) Sometimes they'll just rely on submittals -- here's where good submittals from you WILL make a difference.
My rule of thumb is that a new category for a person needs one "anchor" site and several independent "useful pages."
The "anchor" could be a good official site -- not all official sites are created equal; some would embarress any serious fan, and so are only counted as useful pages; a feature-quality article from Smithsonian or some such magazine (deeplinks accepted), book-length e-text (deeplinks accepted) or some similar depth and quality of content.
The "useful pages" could be in-depth reviews from some authoritative source (deeplinks accepted!), fan sites (that is personal sites, most of whose content is related to the idol/celebrity), or something like that.
These are not official guidelines, but I've been generating personal categories for several years (including some categories where the anchor site was material I had had published) without being chastised. I suspect most experienced Arts editors will use instincts that, if codified, would result in guidelines similar to these. So this, like my reaction to the URLs you listed, should give a more of a feel for the quality of content we'd think worth listening.