1) ζῷον (zōon), meaning "a living being" or "a living animal."
ζῷον appears 23 times in 20 verses, and with the exception of three verses (14:3; 15:7; 19:4), all are found in chapters 4-7. Without exception, every use of ζῷον in Revelation has to do with the four, eye-covered, six-winged creatures which surround God's throne, and who repeat "Holy, Holy, Holy day and night." These same creatures are called seraphims in Isaiah 6:3.
2) θηρίον (thērion), meaning "a wild animal"; or a metaphore for "a brutal, bestial man."
θηρίον appears 46 times in 38 verses. While it appears once in Revelation 11:7, all the rest are found in chapters 13-20. And, every time the word is used, it refers to one of the members of the Satanic trinity: Satan (who would be god - Isa. 14:12-14), the Beast (Antichrist, who causes men to worship Satan - Rev. 13:4), or the second Beast (the False Prophet, who, acting like the Holy Spirit, focuses all attention on Satan and the Antichrist - Rev. 13:12).
We read from Revelation 11 and 13, that the Satanic trinity's three individual created beings (something that immediately reveals the difference between them and the Holy Trinity - The Father, The Son, and The Holy Spirit have existed eternally as one God) each appear from different places.
Satan: "And the great dragon was cast out, that old serpent, called the Devil, and Satan, which deceiveth the whole world: he was cast out (of heaven - Lk. 10:18) into the earth, and his angels were cast out with him" (Rev. 12:9). We read in Revelation 11:7 that he then ascends out of the bottomless pit to kill the two witnesses (Rev. 11:7).
Antichrist: "And I stood upon the sand of the sea, and saw a beast rise up out of the sea, having seven heads and ten horns, and upon his horns ten crowns, and upon his heads the name of blasphemy" (Rev. 13:1). Revelation explains "the sea" thusly: "The waters which thou sawest, where the whore sitteth, are peoples, and multitudes, and nations, and tongues" (Rev. 17:15). In other words, he comes from the Gentile world.
The False Prophet: "And I beheld another beast coming up out of the earth (land); and he had two horns like a lamb, and he spake as a dragon" (Rev. 13:11). Because of his origins and the fact that the idea of "the land" usually refers to Israel, he is believed to be a Jew.
Isn't it interesting that these come from heaven, the sea, and the earth?