Windows 1 to 98 were integrated with MS-DOS in that Windows could not run without DOS. With Windows NT and all its variants, such as XP, Vista and 7, Windows does not need DOS, although it still has DOS-ish ideas built in (backslash pathway arguments, etc.).
UNIX is available in many OS "flavors". Each has specific hardware that it will work with. Mac OS from version 10.5 on is certified UNIX, although it uses a hybrid kernel called XNU ("X is Not UNIX"). Theoreticians claim a smaller kernel design contributes to minimality in privilege code, and thus potentially better security. Linux is a UNIX cousin, not really UNIX, just built very similarly to benefit from the security and power basis of UNIX. It uses a monolithic kernel like most UNIX systems developed from the time of BSD UNIX. Solaris is a certified UNIX system developed by Sun Microsystems (now part of Oracle). There are at least a dozen other variants of UNIX in use in business, education, and government.
By "Z\OS", I suppose you mean Z/OS (only Microsoft uses backslash). That is one of many IBM mainframe systems, not used on home / personal computers.
OpenVMS (Open Virtual Memory System), previously known as VAX-11/VMS, VAX/VMS, runs on VAX (Digital Equipment Corp.), Alpha (Digital Equipment Corp.) and Itanium-based (HP) families of computers.
Some that have gone down the chutes:
-- BeOS, 64-bit pre-emptive multi-tasking, object-oriented, protective memory system when neither Apple nor Microsoft had such. Haiku OS has taken its place. Initially, BeOS was developed only for PowerPC. I have a CD of it that installs on any late PPC Mac and can run four QuickTime movies at once without stuttering.
-- AmigaOS, an amazing performer, especially in graphics, but was officially only intended to run using Amiga graphics chipset, and only on PowerPC.
-- Mac OS "Classic". Ran on PowerPC architecture, used multi-fork files, particularly good with graphics and (consequently) printing and publishing. Lousy with memory management--memory was applied in exact portions to each app and did not change dynamically.
-- NeXT OS (sometimes called "NeXTSTEP"). UNIX-like (like Linux), used the Mach kernel. Acquired by Apple and evolved into Mac OS X.
Above are all for full performance computers. Small devices like phones, iPod, and tablets all use an OS. At any given moment around the world, more computing tasks (Internet surfing, email, instant messaging, writing notes, watching movies, playing music) are performed on these small devices than on traditional computers.