If you're trying to solve one very hard problem, parallelism is not the answer. Recursion is.

Recursion can give you an exponential reduction in error as you descend into the call stack. It's not guaranteed in the context of an LLM but there are ways to strongly encourage some contraction in error at each step. As long as you are, on average, working with a slightly smaller version of the problem each time you recurse, you still get exponential scaling.