olti

Well, I did some benchmarks regarding built-in USB Hub, Samba share write/read, and copying from USBHDD#1 to USBHDD#2.
 
First of all, the file system on the USB Drive made not much difference (about 2MB/s more or less).
Both drives are from WD, one is formated as NTFS (1TB, USB3.0), the other as ext4 (750GB, USB 2.0).
 
As long as I was doing a single write-operation through Samba to one of the USB drives, I got a transfer rate ~30MB/s.
Reading data from the drives by copying them to local machine was about the same speed ~30MB/s.
 
Now, when writing same file simultaneously to both drives, the bandwidth splitted by half for each drive, resulting in ~15MB/s for each drive.
Reading data by the same scenario was also ~15MB/s for each drive.
 
Interesting part was trying local (on Tinker, SSH, rsync) USB Drive #1 to USB Drive #2 copy and the other way around.
There, the choise of the file system gave +/- 2MB/s being somewhere between ~8-11MB/s.
 
As I did the benchmarking, the system was pretty stock only running Pi-Hole in the background, so pretty much all the resources were free.
CPU usage did not climb over 80% by the ntfs-3g driver, so the CPU (max. 1.6GHz on the image used by me) had enough potential.
 
The limiting factor is in fact the freaking USB Hub! As a member of this forum mentioned, ASUS made really stupid move by not soldering one more USB Port, which is provided by the SoC  However, the system is fluent, can deal with my upload speed, and makes fun! Maybe, someone would find this test interesting. Thanks
 
Edit: Just in case, someone wants to know... 5V/2A power supply did not managed to spin up one of the 2.5" drives properly, although the system was stable and did not crash. I've used the RPi3 official supply 5/2.5A, and it powered the board and two 2.5" drives well.

Could be a bad/insufficient/old power supply, bad/counterfeit/mis-inserted SD card, bad/wrong/corrupted image, .... you really should view the serial console[1] to see if there's any useful message or any legible output at all.  If you must fly blind, first try rewriting the SD card, making sure you're using the correct stable image for the board and verifying that it was downloaded, extracted, and written to the card properly.
 
[1] See http://lucsmall.com/2017/01/19/beginners-guide-to-the-orange-pi-zero/ (read the note on the USB-to-serial converter voltage level before the "Software requirements" heading, then skip to "Alternative strategy, using USB-to-serial converter")

You have made the same mistake graphically that I made physically at first. Sorry for not being clear enough.
 
In that picture, you have actually encircled R353/R352. These are _not_ identical to R135/R136. R135/R136 sit directly below the encircled resistors in that picture. R353/R352 can stay, R135/R136 have to go.
 
A correctly modified board looks like this (test if I can include images from the sunxi wiki):
 
I have now corrected the wiki page. I could not replace the image with the wrong resistors highlighted, so I uploaded a new one with a different name and used this in the article to highlight the R135/R136 resistor positions:

Hi,
 
1st OPi Zero (512 MB, heatsink, no case, capped to 768 MHz, room temp 15°C, 2A power supply via USB, ARMBIAN 5.25 stable Debian GNU/Linux 8 (jessie) 3.4.113-sun8i):
20:06:21:  240MHz  0.06   1%   0%   0%   0%   0%   0%   64°C
20:06:26:  240MHz  0.06   1%   0%   0%   0%   0%   0%   63°C
20:06:31:  240MHz  0.05   2%   1%   0%   0%   0%   0%   64°C
 
2nd OPi Zero (256 MB, no heatsink, no case, capped to 768 MHz, room temp 10°C, 1.5A power supply via pin1+2, ARMBIAN 5.25 stable Debian GNU/Linux 8 (jessie) 3.4.113-sun8i):
20:05:35:  240MHz  0.17   2%   1%   0%   0%   0%   0%   60°C
20:05:40:  240MHz  0.16   1%   1%   0%   0%   0%   0%   60°C
20:05:45:  240MHz  0.14   1%   1%   0%   0%   0%   0%   61°C
 
So there seems to be no effect of power supply.
However, it runs 50°C over room temp on idle... I wonder what will happen in the summer
 
To compare: OPi One, heatsink, case, room temp 15 °C, ARMBIAN 5.25 stable Debian GNU/Linux 8 (jessie) 3.4.113-sun8i:
20:11:09: 1008MHz  0.34   3%   0%   3%   0%   0%   0%   34°C
20:11:15: 1008MHz  0.40   4%   0%   3%   0%   0%   0%   35°C
20:11:20:  240MHz  0.37   4%   0%   3%   0%   0%   0%   35°C
 

Hi,
 
1st OPi Zero (512 MB, heatsink, no case, capped to 768 MHz, room temp 15°C, 2A power supply via USB, ARMBIAN 5.25 stable Debian GNU/Linux 8 (jessie) 3.4.113-sun8i):
20:06:21:  240MHz  0.06   1%   0%   0%   0%   0%   0%   64°C
20:06:26:  240MHz  0.06   1%   0%   0%   0%   0%   0%   63°C
20:06:31:  240MHz  0.05   2%   1%   0%   0%   0%   0%   64°C
 
2nd OPi Zero (256 MB, no heatsink, no case, capped to 768 MHz, room temp 10°C, 1.5A power supply via pin1+2, ARMBIAN 5.25 stable Debian GNU/Linux 8 (jessie) 3.4.113-sun8i):
20:05:35:  240MHz  0.17   2%   1%   0%   0%   0%   0%   60°C
20:05:40:  240MHz  0.16   1%   1%   0%   0%   0%   0%   60°C
20:05:45:  240MHz  0.14   1%   1%   0%   0%   0%   0%   61°C
 
So there seems to be no effect of power supply.
However, it runs 50°C over room temp on idle... I wonder what will happen in the summer
 
To compare: OPi One, heatsink, case, room temp 15 °C, ARMBIAN 5.25 stable Debian GNU/Linux 8 (jessie) 3.4.113-sun8i:
20:11:09: 1008MHz  0.34   3%   0%   3%   0%   0%   0%   34°C
20:11:15: 1008MHz  0.40   4%   0%   3%   0%   0%   0%   35°C
20:11:20:  240MHz  0.37   4%   0%   3%   0%   0%   0%   35°C