In the bowl of a food processor or blender, combine lime juice, olive oil, jalapeño, cilantro, salt and pepper.
Pulse until combined.
In a small, nonreactive bowl, combine shrimp, mango, and shallots.
Pour over lime juice mixture, making sure that all shrimp is submerged, and place in refrigerator for 30-60 minutes, stirring occasionally. (Do not let shrimp sit too long in the lime juice – it will begin to break down.)
To serve, cut each cucumber half in half, making a total of 4 pieces.
Place a cucumber boat on plate, and spoon ceviche into cucumber boats.
Garnish with lime zest.