The Magic of Oz is a relatively unknown short five and a half minute Oz cartoon that focuses on Dorothy, the Scarecrow, and Tin Man meeting the Cowardly Lion and is unrelated to the novel of the same name. Its poor quality that includes crude animation and lack of actual plot has lead to it being cited as "the worst cartoon ever" in one online upload.
The first known mention of its existence was in 2010 when animation historian Jerry Beck featured it in a lineup of “Worst Cartoons Ever” at the San Diego Comic Con. His expert guess places it’s creation during the 1960s.
It is unknown exactly what year it was created in with a possibility of it coming after the 1939 film since the ending song is similar to We're Off to See the Wizard. It would appear to be very experimental and can't be linked to any known studio even with names provided of those who worked on it along with the end-credit of "A Cartoon Film Presentation" being rather vague.
The Magic of Oz - The Worst Cartoon Ever