English

Well if we could use any power that equation would be a bit simplier. However, I don't expect any other stat will use ^4 that I know of...

Damage = <DmgFactor>*(26+<quality>+(1/(<quality>^4)))*(1 00+<precraft>)/100

(or if you really enable the power function it could be:
Damage = <DmgFactor>*(26+<quality>+(<quality>^-4)*(100+ <precraft>)/100
)