Hi, @Denise99 , thanks for the question! But I'm a little confused by your reference to "zero tax liability", as that's generally not associated with a backdoor Roth conversion.
The main advantage of a backdoor Roth is that it gives the ability for high earners to put money into a Roth, in spite of the fact that they are above the income limit for doing so directly. The main tax advantage of a Roth in general is that one enjoys tax-free growth. Another advantage is that these contributions (but not the earnings) can generally be withdrawn without penalty regardless of your age.
The main con is that there is no immediate tax deduction for your contributions, but for high-earners this is often a moot point.
Hope this helps!
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"
