Mark "Zibo" Joseph Zbikowski (born March 21, 1956) is a former Microsoft Architect and an early computer hacker.
He started working at the company only a few years after its inception, leading efforts in MS-DOS, OS/2, Cairo and Windows NT.
In 2006 he was honored for 25 years of service with the company, the third employee to reach this milestone, after Bill Gates and Steve Ballmer.
He was the designer of the MS-DOS executable file format, and the headers of that file format start with his initials: the ASCII characters 'MZ' (0x4D, 0x5A).