Blitzcrank vs Zyra

Fire Rocket Grab (Q) from a brush or a side angle: it grabs the first enemy hit, so you need a line without minions.

After a successful grab, cast Power Fist (E) right away: your next auto knocks the target into the air and deals double damage.

Sometimes engage without a grab: rush in with Overdrive (W), knock your target into the air with Power Fist (E), and save Rocket Grab (Q) for when they Flash away.

Use Mana Barrier (passive) to bait: at low health you get a shield based on your mana, enough to make a kill look easy.

In teamfights, save Rocket Grab (Q) for their carry and wait for them out of vision: grabbing them before the fight starts often decides it.

Get out of the line of Grasping Roots (E): the roots pass through minions and root every enemy hit, then her plants hit the trapped target.

Step on her seeds to destroy them before she grows them: Rampant Growth (W) seeds reveal you for a moment, but leave her no plant.

Take down the plants born from Garden of Thorns (passive), or back off until they die: they take fixed damage, like a ward, and don't live long.

Get out of the Stranglethorns (R) zone as soon as it appears: the vines knock you into the air 2 seconds later, and her plants are empowered inside.

If you can engage, go for Zyra when her plants are far from her: the Thorn Spitter from Deadly Spines (Q) only fires at 575 range.