You are making a logic error. Since it has indeed happened on earth which is part of the universe then a zero probability of it happening elsewhere is the universe is voided.
“Since it has indeed happened on earth...”
Life exists on Earth. That much is established. What is not established is that life on Earth arose spontaneously from natural processes. You’ve got to actually establish that fact if it is a fundamental building block of the rest of your argument about the existence of life in the universe.