Python code:

digits = {
    'one': '1',
    'two': '2',
    'three': '3',
    'four': '4',
    'five': '5',
    'six': '6',
    'seven': '7',
    'eight': '8',
    'nine': '9',
}

digits_reversed = {key[::-1]: value for key, value in digits.items()}

def find_first_number(line: str, digits: dict[str, int]) -> str:
    for i, char in enumerate(line):
        if char.isdigit():
            return char
        else:
            for num, value in digits.items():
                if line[i:].startswith(num):
                    return value
    raise RuntimeError('No digits found in string!')

def parse_calibration_value_v2(line: str) -> int:
    return int(find_first_number(line, digits) + find_first_number(line[::-1], digits_reversed))