UB Burst seems interesting: it's weirdly in between being a breaker and a cleaner. Here are some calcs, with Chandelure's stats changed and Overheat as Mind Blown with 150 BP:
For a cleaner set with Scarf:
252 SpA Chandelure Shadow Ball vs. 4 HP / 0 SpD Zygarde: 153-181 (42.7 - 50.5%) -- 2%...