> if you can efficiently find inputs where the output has lots of leading zeroes that's a partial break, and lets you mine bitcoin more efficiently Depends on

> if you can efficiently find inputs where the output has lots of leading zeroes that's a partial break, and lets you mine bitcoin more efficiently Depends on the type of break. If the break only allows finding a hash with 128+k leading zeroes in 2^{128+k/2} time, that would still be quite useless for bitcoin mining. The break would have to cover the bitcoin regime of around 78 leading 0s.