Melana has dark eyes, long black hair, fair skin, and is of Asian descent. She is identical in physical appearance to her twin sister Anaya.
Anaya and Melana are unwaveringly loyal and dedicated to their father Dr. Zin. After his apparent death, they seek revenge against Benton Quest and his family.
Anaya and Melana have their scientist Dr. Hatani design and build robotic assassins, three in all. The first "Zinja" is sent to steal a momentum-increasing invention of Dr. Quest's, but the thief was unknowingly stopped by Race Bannon. Race then impersonated the destroyed Zinja and reported back to Anaya and Melana, who, thinking the mission a success, dispatch the second Zinja to assassinate the President of the United States.
When Jonny Quest tries to contact Race via the comlink he still wore, the Zin Twins overhear and order Dr. Hatani to stop him. Race easily defeats the scientist, but has a tougher time with the third, partially complete Zinja. Race is able to trick the Zinja into accidentally destroying the computer which control the robots, deactivating both the one in the Twins' hideout as well as the one sent to kill the President.
After this, Hadji Singh and Jessie Bannon arrive and fight Anaya and Melana in hand-to-hand fighting and defeat them both. After this, Dr. Zin himself appears, having faked his own death to test his daughters' ability to run his empire without him. He chides them for their failure. Zin arranges a "surprise" for Bannon and the kids (a bomb), and the twins and Dr. Hatani escape aboard their helicopter.