how can i remaster the 17mb zImage that found in XPEnoboot_DS3615xs_5.x-xxxx.iso

[minlearn]

i noticed that from dsm 6.x series, they switched to grub2 bootloader.

 

but in 5.x they still use grub1or syslinux boot loader for ISO booting.

in 6.x the rd.gz and zimage are separated,the zimage sizes keeps at 2-3M

while in 5.x the xpenology favourd synoboot img,iso files,they use a zimage larger than 10mb.no rd.gz found.

 

in https://xpenology.com/wiki/en/building_xpenology it just explains how the zimage recompiled,how the rd.gz, pat be reproduced

in https://github.com/kref/scripts it explains how multi part image file for USB build.

 

what i want to know is,how can i get the > 10mb zimage file reproduced,remastered? while may possblely found in a XPEnoboot_DS3615xs_5.x-xxxx.iso?