The NanoPi NEO 4 is an affordable and compact Raspberry Pi alternative that FriendlyElec equips with a six-core processor and 1 GB RAM. The board has numerous ports and sensors including HDMI 2.0 and USB Type-C too. The NanoPi NEO 4 ships worldwide for US$50.
https://www.notebookcheck.net/FriendlyElec-NanoPi-NEO-4-A-compact-and-hexa-core-powered-Raspberry-Pi-alternative-that-costs-just-US-50.420092.0.html
To get decent performance out of the rk3399, you're going to need good cooling.
This board has been out for quite a while.
The rk3399 has been around for over two years, sadly very little competition until recently, the recent amlogic s922 series looks worthy. New rockchip SoCs are on the at too
One of the primary reason the pi zero is so popular is it's anemic power requirements. At 5v 3a this device is more inline with the B+ variant and seems to be designed to compete with that part. Both are more than double the power consumption of a pi-z, but this nanoPi has an attractive price point that is an interesting alternative.