Let me begin this with; It isn’t impossible to lie to a Sheikah– it is however, very difficult… Or rather, you can try, but it’s unlikely they’ll believe you.
Every Sheikah has the truth-sense, passed down from the First Impa, Hylia’s hand-maiden*. The intensity of the gift differs— were you to lie to Impa herself.. Well, it would be known immediately, where for Prince Zamir, it would be an itch at his mind, requiring him to focus further.
Those who have the strongest Truth-Sense are the ones picked for succession, an often are the ones named Sheikh / trained to be the next Sage.
Zamir’s Truth-Sense grows more refined as he ages, rivaling Impa’s by the time of her ascendancy– where as Zelda-Asheral has very little of the gift** to speak of.
On the opposite end– the stronger their Truth-Sense, the harder it is for a Sheikah to lie— this, in part, is why they speak in vague circles and riddles, and why as a people they are very, very blunt. vague texts from ancient days imply that the first Impa would become violently ill if she were to lie.
Those who see the Truth, but keep the secrets, must trade something for it.
* Sheikah history quotes her as Hylia’s consort, Hylian history cites her as a protector, after the tri-war, a ‘compromise’ was ‘discovered’.
** Impa’s theory is that Zelda’s being the voice of Hylia, a sage in her own right, she has no need for the Truth-Sense in the way Zamir does.