Peel the cucumber and slice in half lengthwise. Scoop out the seeds from the inside of each half. Roughly chop the cucumber and place in a blender.

Cut the avocado in half and remove the pit. Scoop out the avocado and place in the blender with the cucumber. Add the garlic, ground coriander, yogurt, lemon juice, zest, and salt. Puree until the soup is smooth, adding water as needed to reach a soup consistency. Place in a bowl and refrigerate until cool.

Dice the avocado and toss with lemon juice and chili flakes (if using). Divide the soup into two bowls and top with diced avocado and hemp seeds.