Raspberry Pi Zero has two noticeable attributes compared to other Raspberry Pi boards: it’s smaller and it’s cheaper. FriendlyARM has now designed another model for their NanoPi family, that about 25% smaller, although not quite as thin at all due to its Ethernet jack and USB connector, and much faster than Raspberry Pi Zero, with NanoPi NEO board powered by Allwinner H3 quad core processor.
The Wiki is still in construction, and for now only in Chinese, but we can find out that FriendlyARM provides Ubuntu-Core with Qt-Embedded for the board relying on Linux 3.4 legacy kernel. However, Allwinner H3 should get full mainline support in Linux 4.7 or 4.8, so I’m fully expecting the board to be supported in mainline kernel in a few months. The schematics (PDF), and header pin assignments are also available in the wiki.