Welcome to EasyBoot @contract
Quote. "is it possible to make windows 7, 8 & ghost (winPE) multi-bootable DVD iso?"
Unfortunately there is no 'generally solution' how to integrate both Win7 & Win8 to same DVD
In fact, there is no 'quick fix' to this problem
You have to choose only one of these two NT6-systems (Win7, Win8 and Server-2008 are NT6-systems - compare with WinXP as example, which is a typical NT5-system)
So choose one NT6-system and be happy with that...
But that WinPE with Ghost11 can most likely be used with its ISO as it is (no need to extract anything, use ISO of WinPE as it is)
My only concerns is what kind of WinPE we are dealing with
If ISO contains folder 'SOURCES' and 'BOOT' and file 'BOOTMGR', then it is a NT6-system and can be launched directly using ISO-file - do it this way:
1. Copy ISO-file of WinPE to folder 'EZBOOT'
2. Use menu command: run winpe.iso (or whatever name you use to ISO-file)
But if that WinPE-ISO-file contains folder i386, then we are dealing with a NT5-system (WinXP, Server-2003 or similar NT5-system) - if this is the case - you must use my script 'easyboot-iso.script' and tick 'Run ISO From RAM'
You have script-collection below in every post I write in this forum - its completely free for private use
However, my guess is that your WinPE is a genuine NT6-system and can run directly from ISO-file (no need to use my script)