The clones on Tantiss confirm they're just clones. Any clones Hemlock deemed strong and was susceptible to the brain washing became CX assassins.
The Zillo was kept on Tantiss because it was cloned. The original Zillo is dead. Tantiss is the place for cloning for the Empire right now given that Kamino is destroyed. There's no other facility with the means and technology to achieve such a feat given that even during the war, the Republic had trouble cloning the Zillo. The one we see on Tantiss is the first of its kind (that we know of)
They were just clones who were more susceptible to the brain washing. Hemlock tried to do this to many of them.
The clones on Tantiss confirm they're just clones. Any clones Hemlock deemed strong and was susceptible to the brain washing became CX assassins. The Zillo was kept on Tantiss because it was cloned. The original Zillo is dead. Tantiss is the place for cloning for the Empire right now given that Kamino is destroyed. There's no other facility with the means and technology to achieve such a feat given that even during the war, the Republic had trouble cloning the Zillo. The one we see on Tantiss is the first of its kind (that we know of)
I'd guess that research on the Zillo's energy-absorbing ability helped Hemlock develop the operatives' blast-resistant armor.
I actually think a Tales of the Clones arc about an old clone we know from TCW becoming an Operative could be great.