Kha'Zix vs Zyra

Jump on an isolated target with Leap (E), then Taste Their Fear (Q): with no ally nearby, Unseen Threat (passive) marks them and the spell hits much harder.

In teamfights, cast Void Assault (R) to vanish and reposition: the invisibility triggers Unseen Threat (passive), and your next auto damages and slows.

Detonate Void Spike (W) close to you in the jungle or in teamfights: you heal if you're inside the explosion area.

Pick your evolutions to fit the game: evolved Leap (E) resets on each takedown, evolved Taste Their Fear (Q) gains range and a lower cooldown on isolated targets.

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.