Just want to apologize for my English, , translate through Google (so for me faster)
RockChip allows you to install the image from Linux directly to the emmc, but for this you need to do operations from the computer on which Linux is installed.
Here I compiled an archive with the necessary scripts, I've already laid out it on 4pda.ru
You may need to install any of the packages listed on page 7. (http://opensource.rock-chips.com/images/d/d5/RK3328_Linux-Debian_V1.1_Development_Guide-20170711.pdf)
The tv-box should be in the mode of the maskrom.
I tried on the original z28 and I ran without a problem the last image from Rosk64 (