I use the following type of grub4dos stanza to boot directly from Tinycore and Microcore ISOs:
title microcore
find --set-root /microcore.iso
map --mem /microcore.iso (hd32)
map --hook
map --status
kernel (hd32)/boot/bzImage quiet ssh tce=hda1
initrd (hd32)/boot/microcore.gz
boot
The key parameter is --mem on the first map statement. That parameter tells grub4dos to simulate a CD by loading the ISO image into (contiguous) memory. Without that parameter, I do not believe that map will work unless the ISO image happens to be stored in contiguous blocks on disk, which is typically not the case. The kernel and initrd commands can be replaced by "chainloader (hd32)" to boot to the menu on the ISO.
The "find --set-root" command is useful since it causes grub4dos to set as the root partition the partition on which grub4dos locates the specified file.