Add mango, pineapple, pineapple juice, and lime juice to a blender. Puree until smooth.
In a medium bowl, combine the coconut milk, agave, and lime zest.
Alternate layers of the mango-pineapple puree and coconut mixture in your popsicle molds. Use a bamboo skewer or long toothpick to swirl each popsicle to create a marble effect.
Cover the mold and insert popsicle sticks. Freeze at least 4 hours, or preferably overnight to set.
Run hot water around the mold for 30-45 seconds to help release the popsicles. Enjoy!