Zoe vs Zilean Counter Pick

Both champions have a 550 attack range and both deal magic damage, so the matchup comes down to one thing: which of them turns a landed skillshot into a kill. Across 151 support games on patch 16.13.1, Zilean is the one who manages it, keeping Zoe to a 39.1% win rate even though he has less base health (574) and less armor (24).

Chronoshift explains most of it. Zoe needs one burst window to win: she puts the target to sleep with Sleepy Trouble Bubble, strips magic resist, then lands an empowered hit from a fully travelled Paddle Star!. A revive cast on that target undoes the entire sequence. Rewind adds to the problem by shortening the cooldowns of his other basic abilities, which lets Time Bomb come up about twice as often as usual, and a double bomb both stuns and deals damage. Time Warp finishes the job by either slowing Zoe out of reach or hasting an ally past her damage entirely.

Zoe pulls ahead in the late numbers: 2,432 health against 2,206 at level 18, 340 move speed against 335, and 58 base attack damage against 52. None of that counts for much when each kill attempt gets reversed. The practical approach is to go after Zilean himself rather than the carry he is protecting, and to use Spell Thief charges gained from his summoner spells to close the gap. The full ability list is on the Zilean page.