Has anybody managed to set up successfully a GS following this steps on a RPi A+? is it possible? and with a RPi zero??
I suspect a Zero (single core) would be too underpowered.
The new Pi model A+ (which I think has the same CPU as a 3B+?) may work, but untested…
As @vk5qi said, the single core Pi Zeros are not powerful enough. They have just a little more cpu power than the original Pi 1 serie.
For the Model A+, it depends on which. There was the original ‘Raspberry Pi Model A+’, which is not powerful enough, and there is the newer ‘Raspberry Pi 3 Model A+’ which works fine. As you mention it along the Pi Zero, i suspect you mean the original single core Model A+ from 2014.
To make it simple: Any Pi 3 or Pi 4 is ok. Original Pi or Pi Zero not. Pi 2 might just be enough, not sure, wouldn’t try unless you still have one around to do a quick test.