A double 3 turn and a Twizzle in Ice Skating are the same thing except for a few minor details.
A Twizzle should have a continuous and unbroken rotation similar to a spin, it should travel and there should be no knee action between each half rotation.
As we begin to learn the sensation of joining a forward and backward 3 turn we will likely have a turn that is somewhat between the two skills.
With more practice and refining our technique, we will begin to separate the skills more clearly.