He posted them here http://boards.na.leagueoflegends.com/en/c/gameplay-balance/EjtVw5RB-meddler-what-exactly-did-the-zyra-ai-tweaks-touch-up-on?comment=0000
<quote>
Zyra's plant logic will not be that much different. Here's the actual logic for those curious:
- Units that have taunted the plant (e.g., Shen), whatever their range.. they will just stare at an out of range unit while taunted
- Champs Zyra has auto-attacked in the last 3 seconds (prioritizing most recently attacked)
- Champs that have recently been attacked by any plant (prioritizing nearest)
- Champs within 350 units of the plant -- for reference, 350 is the size of Lee Sin's E1 or Evelynn's R (prioritizing closest)
- Non-champs Zyra has AA'd (prioritizing most recently attacked)
- Any unit in range (prioritizing closest)
The changes in 5.18 are that:
2 and 5 now use "most recent" over "closest", allowing Zyra to better re-direct plants to higher priority targets;
Plants will no longer get hung up on invisible targets, such as champions in fog of war;
Plants will no longer sometimes mis-believe that they attacked on spawn (which caused a long delay before their first real attack);
Plants will quickly move to face the target they are going to attack next, so you can get a better sense for how your actions shape their priorities.<quote>