In a large pot, heat the olive oil until shimmering.
Add the leek and poblano and cook over moderate heat, stirring, until softened, about 8 minutes.
Add the zucchini and garlic, season with salt and pepper and cook, stirring occasionally, until crisp-tender, 5 to 6 minutes.
Add the chicken broth and Parmesan rind and bring to a boil.
Simmer over moderate heat until the zucchini is very tender and not longer bright green, about 15 minutes. Discard the Parmesan rind and add the chopped cilantro.
Working in batches, puree the soup in a blender or food processor until very smooth. Return the soup to the pot, whisk in the créme frâiche and reheat gently if necessary. Season the soup with salt and pepper and ladle into bowls. Garnish the soup with the cilantro leaves and serve.
The soup can be refrigerated overnight. Reheat gently or serve cold.