I don’t know what you/they did, but that does not line up with my experiences at all.
Zenes are so potent and dosed so fucking low that there’s literally no way they can burn that badly. They’re not the same as xylazine (tranq) at all, which does burn.
There’s also multiple different kinds of them available, all dosed at less than 10mg, even if you’re using 5g of street F a day. Even injected I never experienced burning.
They aren’t something even the most extreme junkie can just snort a line of.
Source: been regularly using various nitazenes via multiple ROAs for multiple years.
You could try spirobrorphine, it’s not a zene and is around pure F potency (a few mg for even the most tolerant street user). That’s a hard one to locate though.