Prepare the white chocolate: In a microwave-safe bowl, melt 1 1/2 cups of white chocolate chips. Heat in the microwave, stirring every 30 seconds until fully melted and smooth.
Coat the cereal: In a large bowl, add 5 cups of Rice Chex cereal. Pour the melted white chocolate over the cereal and gently stir to coat each piece evenly.
Mix the dry ingredients: In a separate bowl, combine 1 cup of powdered sugar, 1 package (3.4 oz) of instant lemon pudding mix, and 1 tbsp of lemon zest. Stir until well mixed.
Combine the mixtures: Sprinkle the powdered sugar mixture over the coated cereal. Toss carefully to ensure all pieces are covered.
Add the lemon juice: Drizzle 1/4 cup of lemon juice over the cereal mixture for an added tangy flavor, and gently toss to combine.
Allow to cool: Spread the mixture out on a baking sheet lined with parchment paper. Let it cool completely before serving, allowing the coating to set.