Ok i've some success with jffs2
i can mount initrd.bin, or even modify the tar.gz file
and i've found a bin to mkfs.jffs2 the result
i've just to try this last operation and flash the result to try it on the Z
anybody knows the exact syntax to make the initrd.bin?
i ask because i've read that you need to specify the offset of the first block you want to write on the flash, and i don't know this offset
also, if there is some success, there'll be a 38mb big file to host for others, if someone have a host to serve that, please contact me