Check for collision of the first few chars

[HMNiLK]

Hello,
I just wanted to know how to crack for one possible solution of a hash following a specific pattern, for example:
(SHA1) 000000XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX -> $(known salt).$(unknown integer), X's can be anything.
Now I just want Hashcat, when looping through the possibilities, to check only if the first n characters of the hash are 0's, and dont check the rest. How do I archieve that?

Thank you!

[atom]

You need to modify the kernel