Asimov's 3 laws are pretty watertight as these things go. Like anything, if implimented incorrectly they can lead to disaster, but when implimented correctly there's no real room for error.
And understood. It was the bane of Dr Calvin's life that other humans did not understand how their systems would behave under human instruction. (Related, though obviously 1stLaw-less, HAL's interpretation of how best to succeed at the mission while keeping the objectives secret, leading up to the respective fates of the crew of the Oddyssey.)
Of course the zeroth law throws everything out of whack, but then again if i recall it was only applied to show that robots, when released from the constraints of the 3 laws, can still be perfectly functioning 'people' in society.
I saw the Giskard/Daneel Zeroth law incident as slightly different, though if you're talking about the Evitable Machine (I think it was) "revamped first law" version, or another incident, I must profess I can't quite remember the relevent plots.
With Giskard and Daneel, Giskard is 'broken' enough to contemplate the Zeroth law, and while he couldn't directly apply it, can
just about implement it within Daneel's matrix so that Daneel can do The Good Work that Giskard couldn't quite have done.
The above from memory (a couple of decades have passed, and I may have slept since). I stand to be corrected on various points.