If you have a mystery situation set up and the party has a solution that cuts right to the end, I don't see the problem. My feeling is, instead of figuring out ways to force people into your line of roleplaying, play into their solution and let them feel good about it.

I've only used ZoT on PCs. And it's great - the character was being questioned by police so they had to prevaricate and choose their words carefully.

I'm not sure how I'd play it if the players had access to ZoT. It could definitely suck the energy out of a plot arc. It'd have to turn from did X do it? to how will we bring X to justice?