You are given a code:

def main_solution(x):
    return func_20(func_15(x), func_5('cvr', 'mu'))

Can you predict the output of `main_solution("zbzenfvnbl")` without writing any code? Please reason and put your final answer in the following json format: {"output": <your output>}, where <your output> should be the final string.
user
{"ref_input": {"x": "zbzenfvnbl"}, "ref_output": "\u00abmzu\u00bbc\u00abvbr\u00bb\u00abz\u00bb\u00abe\u00bb\u00abn\u00bb\u00abf\u00bb\u00abv\u00bb\u00abn\u00bb\u00abb\u00bb\u00abl\u00bb", "ref_code": "def main_solution(x):\n    return func_20(func_15(x), func_5('cvr', 'mu'))", "funcname": "main_solution"}
rule