> 1. From level 2, focus on your root : E + W :

With Aftershock rune : you will have a shield when you root with E.
With Font of life rune : ADC will heal himself hitting the rooted ennemy.
Once again : Zyra does not need agressive runes to deal dammage, these defensive runes will help you to be close enough to E ennemies.

> 2. Harass with Q + W to deal dammage :

At botlane in early : create your plants behind their minions wave, Q should be on ADC and/or supp in order that your plants focus champs and not the minions wave.
If their ADC does not know Zyra, he will try to destroy your plants, which is good for you because range champ need more than one hit to destroy the plant (Melee champs should manage destruction of plants because they can one shot it)
Then with Liandry item, harrassement will be cancer...

> 3.Using Rylai : slow them easly with Q + W :

You can use it to escape or enguage in teamfight when minions are not in range.
When you have Rylai (you can choose it early if your team is in bad position) you can slow them very easily with your range plants. They can't miss the target!

> 4. Best way to ( Q + W ) or ( E + W) :

Always create your plants W after the begining of your root E or Q. In that way, you can choose the position of your plants at the last moment. If ennemies are too far away, don't create seeds/plants. You will learn fast from how far your Q and E can create the plants (you don't need to be precisely on the seed).

> 5. Vision :

Don't forget that your plants give vision! A Q + W in buch will give you vision and hit the ennemy if is here.

> 6. Your simple full combo :

E + W + R + Q + ignite

> 7. Ultimate :

Don't hesitate to use it in defensive way to save you or your team.

> 8. More interesting details :

https://leagueoflegends.fandom.com/wiki/Zyra#Pets