Mecha is non-mechanical sentient beasts called Chi Beasts, which is based on creatures of Chinese mythology.
The Red Dragon Thunderzord is fully robotic constructs, displaying no sentience whatsoever. The Zord itself is based on creatures from western mythology.
This mecha fought on its own for the first five episodes. The rest of the Chi Beasts appeared in the sixth episode.
All five Thunderzords appeared together during their debut.