Line a baking sheet with parchment paper and set it aside.
In a medium saucepan over low heat, melt the white chocolate chips and unsalted butter together, stirring continuously until smooth.
Once melted, remove from heat and mix in the lemon juice, lemonade drink mix, and lemon zest until well combined.
In a large mixing bowl, pour the Rice Chex cereal. Carefully pour the melted lemon mixture over the cereal, using a spatula or fork to gently toss and coat the cereal evenly.
Once coated, sift the powdered sugar over the mixture, gently stirring until all pieces are evenly dusted.
Spread the coated cereal onto the prepared baking sheet in an even layer and allow to sit for at least 10 minutes to set.
Once set, break apart the puppy chow into clusters and serve.