Zyra Mid > Zyra Support
Think about it.
Zyra's really only useful in support because of her 1.5 second stun, and her ult's knockup that can easily be escaped.
Zyra in mid is a lot better, because with thunderlords, Zyra can poke like hell safely. Her laning phase is extremely good. she can stop anyone from farming by just placing a few plants and Q'ing. Once poked enough, she just has to use her EQR Combo with a few plants nearby and It's an instakill. Once she's fed enough she can oneshot people easily. She's also great against tanks because of her plants