Zyra Mid in 7.24
The Plant HP changes are really odd to me im honest and i dont think it fulfills whatever you were aiming:
You basically doubled her HP, but also doubled (even 4x vs T-Spells and Melee-Autos) the damage she takes from other resources except minions and DoTs, while the plant HP doesnt even scale anymore. If the enemy is bad of course it wont matter. But, her plants will never do more than one attack if the enemy has a clue of what he is doing. Cass already has an easy time clearing Zyras plants with Auto -> E. It even requirest less skill and brain than before, since a simple E kills the plant at no cost the entire game.
Zyra's waveclear is so much dependend on her E+Q, that it doesnt even matter for all midlaners to use a skill for her plants. If Zyra uses E to clear, she cant all in her enemies. She needs 2 points in E, to have a safe knock-up at level 6 (one point less in Q for trading/waveclearing). Her W is a seed, which needs either Q or E to spawn a plant. Zyra's Q shape doesnt allow her to effectively waveclear all minions and ofc not if she wants to use it as a trading tool.
She will have to use Q or E anyway to spawn the plant in the first place. She wont be able to push and punish the enemy laner for using a skill for her plant. And on PBE almost every mage will kill them even faster than before:
Cassiopeia (E), Taliyah (Q /grounded with auto for even less cost), Viktor (Q), Leblanc (Q), Ryze (Q-E), Vladimir (Q), Velkoz (W), TF (W), Annie (Q), ASol (P+Auto), Ahri (W), Galio (Auto) literally every single Assassin, too, will just oneshot her plants in lane. The DoT changes are the only good ones, but even those wont matter that much. Because Malz presses E on a plant, autos it and keeps waveclearing with it. Syndra will use her plants for her own waveclear with W anyway. Its really easy to play around Zyra's cooldowns in the midlane with her 2 basic abilities.
Your changes make sense in theory, but the way her potential matchups and Zyra herself are designed its not going to work out, i can tell you that already. You need to give Zyra additional waves to waveclear or all of this is just a straight nerf.
Overall these changes are only good for waveclearing a pushed in wave before it hits your own tower, since plants are 2x as tanky against minions now. But, if you didnt change anything about her plant HP and gave her plants 2x attackspeed vs minions, the result wouldve been the same in this case and better in any other situation.
All of Zyras damage is balanced around plants. So dont make the enemies just onehit them with single target spells.
now being viable on her due to this, she has a lot of oppressive poke, but she's super squishy and immobile, so if she misses her spells she'll get punished by dying, but sure, her plants get one shot, so angle your Q so they are at a range, E plants are rendered useless except for providing a slow for 1 or 2 autos. Q plus 1 plant clears the backline in the early game and her E clears it by itself at rank 4. She scales pretty hard into mid and late game if she's peeled for, her ability to both peel and provide consistent DPS in teamfights not only makes her a viable mid pick now, but a meta one at that. Zyra is currently sitting as the #5 Mid laner on OP.GG in Platinum +. The date of this post is 12/14/2017