success 
I managed to make I.INSERT-1.3.9 II.PARTEDMAGIC-1.7 III.SLAX-5.1.8 cooperate
i left out ubcd (dos) because it is like a gordian knot for me.
after hours and hours of efforts I found how it should be
1. firstly, no "isolinux" folder must be left (un-renamed) in multiboot root because isolinux-based-distributions are confused, look automatically for "isolinux" folders and ignore their own boot-loaders.
1.1. So... rename "isolinux" folder of insert to "inlinux" (or whatever you like ie. ducklinux)
1.2. Likewise... rename "isolinux" folder of partedmagic to "gpalinux"
1.3. Optionally... rename "boot" folder of SLAX to "slax". Do it only if you want to include dslinux/ koppix / kanotix which have a homonymous folder. You also have to replace the references in the "isolinux.cfg" file.
*** don't hexedit any "isolinux.bin" file other than that founds in "ezboot" folder because checksum errors appear.
2. secondly, put contents of the three distros in the same root (ie. eazyboot/disk1). Only "isolinux" folders (of INSERT & PARTEDMAGIC) have to be renamed. Leave "base" folder as it is. Remove some obsolete empty folders and html files.
*** u don't need to extract any boot-loader from the initial iso with ultraiso. i mean you don't need files such as "slax.bif" or "insert.bif"
3. use the ezboot-commands below to make them run
3.1. for SLAX
CODE
bcdw /slax/isolinux.bin /slax/vmlinuz max_loop=255 initrd=/slax/initrd.gz init=linuxrc root=/dev/ram0 rw
3.2. for INSERT
CODE
bcdw/inlinux/isolinux.bin /inlinux/vmlinuz initrd=/inlinux/miniroot.lz init=/etc/init nomce noapic dma boot_image=insert
3.3. for PARTEDMAGIC
CODE
bcdw /gpalinux/isolinux.bin /gpalinux/bzImage noapic initrd=/gpalinux/initrd.gz root=/dev/ram0 init=/linuxrc ramdisk_size=100000
* in the files "isolinux.cfg" is all the magic you need to make commands work. every distro has its own cfg file . I have read that some guys merged these cfg files but i can't make it right.
*** i have no idea about linux file system, the job above was done by experimenting, googling, searching, trying, trial & error. So, if any linux guru finds mistakes in my job, i don't care since it works for me.
