Hubzilla is primarily a decentralised content management system and community server which just happens to include decentralised social networking and an integrated decentralised permission/access system. This works exactly the same whether you're viewing a fediverse post, a wiki page, or a "for your eyes only" sex video uploaded by your girlfriend.
Some have complained that Hubzilla tries to do too much, but we were mostly seeing what kinds of interesting applications one could build using decentralised technology with cross-domain single sign-on and decentralised permissions. (Spoiler - nearly anything; this is how the internet should've worked in the first place).
Zap is primarily a fediverse (social network) server and is what I have invested the bulk of my time on over the last year or two. It's tuned to work best as a fediverse platform and provides features which are more applicable to that use case rather than for content publishing and web page layout (for instance). We've probably put a lot more effort into privacy and abuse prevention than most fediverse projects, but none of this matters as we're not competing with anybody. It's just something I feel compelled to do.