from xpinyin import Pinyin

def generate_english_name(chinese_name: str) -> str:
    """
    Generate english name from chinese name.
    Rule: Surname initial + First name full pinyin.
    Example: 张三 -> zsan
    """
    if not chinese_name:
        return ""
    
    p = Pinyin()
    # Assuming first char is surname
    surname = chinese_name[0]
    firstname = chinese_name[1:]
    
    surname_pinyin = p.get_pinyin(surname, "").lower()
    firstname_initial = p.get_initials(firstname, "").lower()
    
    return f"{surname_pinyin}{firstname_initial}"