from typing import List


def ls_elements_replace_strings(ls_elements: List[str], s_old: str, s_new: str) -> List[str]:
    """
    führe ein <str>.replace(s_old, s_new) in allen Elementen der Liste durch, welche vom Typ str sind

    >>> ls_elements_replace_strings(['a', 'b', 'c', 1], 'a', 'z')
    ['z', 'b', 'c', 1]
    >>> ls_elements_replace_strings([], 'a', 'z')
    []

    """

    if not ls_elements:
        return ls_elements

    ls_results = []
    for s_element in ls_elements:
        if type(s_element) == str:
            s_element = s_element.replace(s_old, s_new)
        ls_results.append(s_element)
    return ls_results