keep trying people for heresy and the province's zeal will go up but no inquisitions.

this is how you can boost zeal of a province without disatrous results.

as for spanish, if you can't fry their generals, just park the inqs in the provinces.

people will die as the inquisition spirals out of control and this reduces the agricultural income which is what powers the Spanish economy in many cases.

play havoc with rival factions using inqs.

I've once had a Europe as the French in which no catholic other than me had more than a 0* general and half of the factions were eliminated and grey.