Zapcc speeds up incremental builds of a single translation unit. And it speeds up clean-cache builds that include the same headers in multiple translation units. Ccache does not. Yes, this is a huge advantage in real situations.

Frankly your attitude in this whole thread has been very condescending. Being condescending and also not understanding what you're talking about is a really bad combination. Reconsider whether your commenting style is consistent with the HN guidelines, please.