IPA: /ˈzɛstfəli/
KK: /zɛstfəli/
In a way that shows great enthusiasm and energy.
She approached her new project zestfully, eager to make it a success.
Zestfully → It is formed from "zest" (from Old French *zeste*, meaning a piece of citrus peel used for flavor) and "-fully" (meaning in a manner full of). The word "zestfully" means in a manner full of enthusiasm or energy, akin to the lively flavor that zest adds to food.
Think of 'zest' as adding a lively flavor to something, and remember that 'zestfully' means doing something with full enthusiasm and energy.