Slice the zucchinis about 1/4 inch thick. Blanch them by cooking them for 5 minutes in boiling water. Transfer immediately to a bowl with ice water. This stops them from cooking.
Line a baking tray with parchment paper. Then arrange your zucchinis in single layer and freeze them for at least 2-3 hours. Once frozen, transfer to a freezer bag or container.
To make the smoothie:
In a high-power blender, add all your ingredients and blend until smooth and creamy. If too thick, you may add more liquid or ice.