After 2 years will be looking for another WC players to replace him, leaving us in the same situation as of now.
No to Zingaro, better get someone younger that will give this team 5 or 6 years and some value if we decide to sell him.
We'd do that imo if we can buy such a player. The problem is that this younger striker has to be a top striker because everyone expects immediate impact and tons of goals. For such a striker there will be lots of interested teams, and we'll probably lose the battle to some City, PSG or Real. On top of it, this younger striker will be at least twice more expensive than Zlatan (Cavani for +60m eur or something) and will require similar wages.
It still seems impossible to sign Zlatan, but make no mistake that if we can sign him, that's the best we can do. It's nice to discuss how Cavani, Suarez, Aguero, Benzema or Falcao will be better signings than Zlatan, but it's another thing to sign them.