We're all aware of Zlatan's age but I also know that Zlatan is a rarity when its come to performance relative to age. He's a freak of nature considering his performance level at this age, and he's showing no signs of slowing down. His athletic decline has been minimal and he's actually having one of his best ever seasons right now (36 goals, 14 assists in 39 appearances). He's not going to have it as easy he does in the Ligue 1, but let's not make the mistake of overrating EPL, which isn't as strong as it used to be. Also, I don't get the comparison of Zlatan to Schweinsteiger, they're very different situations. Schwieni's fitness issues and physical decline are on a different level than Zlatan, despite him being 3 years younger than Zlatan. All that shows is that not all players decline in the same way. Schweini was already struggling with fitness issues well before we signed him, that's why we knew it was a risk.
Kane is a really good player but it's incredibly difficult to go after him this summer. It's just not the right time; Spurs will finish above us, we might not even have CL, and Spurs will want a record fee for him regardless (Levy won't even want to sell him to us). That's why Zlatan works as a short term solution on a 1 or 2-year deal as a FREE transfer, and after 1-2 years, we can go after Kane. Zlatan comes in and instantly makes us title contenders in the league. That makes far more sense.