i dont think this at all. it wouldnt make sense.
1. Maddness of king Scar controdictes all facts of Scar succesfully seducing Nala
2. If it was this would be rape and i doubt Simba would of let Vitani live past the age of 1 let alone 5
3.I doubt Scar would be strong enough to seduce Nala to attualy have a cub.
4. Age. Nala would of had to have Vitani before CYFTLT meaning Vitani would be in TLK and also be alot older in SP
so Zira it will have to be