Hm. Zilean would be loreOP if he could drift to and fro voluntarily and along other peoples timelines. There would be no secrets anymore. From the line, "The most torturous aspect of this curse is that Zilean sometimes experiences Urtistan as it once was and the rest of the time resides in its lonely ruins," I take that its certainly an unfortunate disease and not a super power. He would never have to 'reside in its lonely ruins' had he the option to spend his time enjoying the vivid histories of his colleagues; Sampling the thrilling dogfights in Corki's past, or winking at everyone next time hes in a match with Garen 'n Kat.
Nevertheless he Was a quite powerful sorcerer of time. Hes the best suited to help that comes to mind, assuming His mind ever comes to the present long enough to do so.