The [Z] chord just means strumming with one hand while you cover your strings really lightly with the other hand that you form your chords. Creates a percussive sound as used by CCR in this song. We'll try it a few times. If it doesn't work, we'll revise the arrangement.

"Lookin' Out My Back Door" is a song recorded by the American band Creedence Clearwater Revival, also known as CCR. The song was written by the band's lead singer, guitarist, and songwriter, John Fogerty. The song is included on their 1970 album Cosmo's Factory, the group's fifth album, which was also their fifth and final number-two Billboard hit.

"Lookin' Out My Back Door" was a direct tribute to the Bakersfield Sound, a form of music that influenced Fogerty and the CCR sound. Buck Owens, one of the architects of the Bakersfield Sound, is even mentioned in the song's lyrics. Fogerty, has stated in interviews that the song was written for his then three-year-old son, Josh. Fogerty has also said that the reference to a parade passing by was inspired by the Dr. Seuss book And to Think That I Saw It on Mulberry Street. (Wikipedia)