```python
def combine_fractions(parts: list[str]) -> str:
    from fractions import Fraction

    if not parts:
        raise ValueError("Input list cannot be empty")

    total = Fraction(0, 1)
    for frac_str in parts:
        try:
            numerator, denominator = frac_str.split('/')
            numerator = int(numerator)
            denominator = int(denominator)
            if denominator == 0:
                raise ValueError("Denominator cannot be zero")
            if '/' in fraction or '-' in fraction[0] and not fraction.startswith('-'):
                raise ValueError("Invalid fraction format")
            total += Fraction(numerator, denominator)
        except (ValueError, IndexError):
            raise ValueError("Invalid fraction format")

    return str(total)
```