In a medium saucepan, melt the white chocolate chips over low heat, stirring constantly to prevent burning. Once melted, remove from heat.
Stir in the thawed lemonade concentrate and salt until well combined and smooth.
In a large mixing bowl, add the Rice Chex cereal. Pour the melted lemonade mixture over the cereal, and gently stir to coat all the pieces evenly.
Once coated, sprinkle the powdered sugar over the mixture, add lemon zest, and toss until well coated.
Spread the mixture in a single layer on a baking sheet lined with parchment paper to allow it to cool and set for about 10 minutes.
Break into pieces and serve immediately or store in an airtight container.