Captain Mutiny was only a side-villain, just appearing for a few episodes. And was the third villain boss to appear after Scorpius and Trakeena.
Captain Zahab was a remorseful pirate captain, who merely scolds his underlings, if they either fail, or betray him.
Captain Mutiny was a remorseless, pure evil, pirate captain, who captures, and sometimes, kills some of his slaves, and either, scolds, or physically abuses his underlings, regardless if they fail or betray him.
Captain Zahab desired to awaken Daitanix in order to destroy the Earth and turn it into a jewel.
Captain Mutiny wanted to loot Terra Venture and enslave the people.
Captain Zahab was sealed away for 3000 years by the past Gingaman
Captain Mutiny was locked within the Lost Galaxy; never had any association with Earth or Terra Venture
Captain Zahab was destroyed by the Black Knight and the Gingamen in an all-out battle.
Captain Mutiny was destroyed by Trakeena who destroyed his castle.
His left hand was cut off by the First Generation of Ginga Red and replaced with a Hook.
His Hook hand incident is unknown.
He will never get killed by Steerwoman Shelinda, because She is very loyal to him and followed his orders.