From execution time perspective:

For every additional leading zero in the hash, it will approximately consume 16 times more. For e.g. finding one zero takes 10 ms, then finding 3 leading zeros should take 16^2 * 10 ms.

I have also published an article using Python in Medium to get leading zeros upto 10X faster.

You can visit here:

A Fast Approach to Finding Strings with Leading Zeros in SHA Hashes!