Replace default kernel in an ISO


I would like to replace the existing kernel (kernel-default-4.12.14-94.41.1.x86_64.rpm) in the ISO with one which i compiled .
i replaced the kernel RPM files in the SLE-12-SP4-Desktop-DVD-x86_64-GM-DVD1\suse\x86_64 folder and renamed them as the original file .
and then used mksusecd to create another ISO.

While installation, installer shows a check-sum error mismatch but allows to ignore and proceed .
with this, the PC is booting with the modified kernel .

But I dont think this is the right process .

could someone guide what is the right process for the same ?