You are given a code:

def main_solution(x):
    return func_20(func_1(x, 4), func_15('vpmal'))

Can you predict the output of `main_solution("zuzjgbztw")` 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": "zuzjgbztw"}, "ref_output": "z\u00abuvz\u00bbj\u00abgpb\u00bbz\u00abtmw\u00bbz\u00abuaz\u00bbj\u00abglb\u00bbztwzuzjgbztwzuzjgbztw", "ref_code": "def main_solution(x):\n    return func_20(func_1(x, 4), func_15('vpmal'))", "funcname": "main_solution"}
rule