Zilla

 The original Zilla is seen in the first episode which begins the same way the 1998 movie ended, with his death. He later on was resurrected as Cyber-zilla.

Godzilla: Final Wars   

 A Zilla under the control of the Xilians attacks Sydney, Australia. He is then defeated very quickly by Godzilla(the fight it's self only lasted about 13 seconds, the fastest fight Godzilla ever had). Which Zilla it was is unknown though it's probably a new one assuming "Godzilla: The Series" is in canon. If so it can't be the original since it was killed and later resurrected as Cyber-zilla, it also can't be Zilla Jr. since he is immune to mind control under normal conditions as well as a better fighter then all previous Zillas. So it is probably a new character, maybe it was another surviving baby Zilla from "Godzilla(1998)".  
Homage
  As mentioned above the entire Zilla species was originally called Godzilla, this is because they were ment to be an alternate version of Godzilla. This would naturally mean that there are lots of homages to the original Godzilla. Such homages are being mutated by nuclear means, large spikes(though they are different in shape), coloring, a  Amphibious nature(they even swim the same way) and though Zilla isn't a mutant dinosaur like the original he does resemble one. The Zillas may also have a homage to Spacegodzilla since it's largest spike is in a more cone shape and is near the shoulder like it. 
Trivia 
*In the 1998 movie Nick Tatopoulos states before zilla is discovered that he is a hybred, suggesting that he is not truly a mutant marine iguana