Has anyone had good results on overclocking the PiZero? If so what speeds where achieved?
The Pi Zero uses the same silicon as Pi 1, so they have the same top speed 1GHz. Pi 1 came with a more conservative clock speed but Pi Zero came already maxed out, so it makes no sense to overclock Pi Zero (but on the other way Pi 1 should be able to be cranked to Pi Zero levels.)
According to a comment on the Pi Foundation's blog post announcing the recent Raspbian update, due to a bug you should not overclock your Pi Zero. It will actually slow it down.
Simon Long says: 2nd Dec 2015 at 1:57 pm
On Pi Zero, you should just leave overclocking set to “None” (which selects the default clock speeds set for the device in the firmware, i.e. 1GHz on the Zero) – all the other options will actually slow your Pi Zero down! This will be corrected in the next release – Pi Zero basically comes out of the box running as fast as it is safe to run it.
I think you can overclock it but it is actually underclocking if you overclock with the default settings because they are for the Pi 1 which has a slower default clock. If you edit config.txt you may be able to go higher but if you want to be really safe use a heatsink.
I have overclocked my Pi zero w upto 1.1ghz at 47 degrees celsius without any heatsink or cooling fan. It is possible to overclock without any cooling upto 1.5ghz(i cannot provide the source, it is a portuguese website where people have competitions on overclocking the pi). The highest reached is 1.62ghz with water cooling. Just fiddle with the config file!(you might damage a few sd cards in this process)