def zeros(r, c=None, cls=None):
    """Returns a matrix of zeros with ``r`` rows and ``c`` columns;
    if ``c`` is omitted a square matrix will be returned.

    See Also
    ========

    diofant.matrices.dense.ones
    diofant.matrices.dense.eye
    diofant.matrices.dense.diag

    """
    if cls is None:
        from . import Matrix as cls
    return cls.zeros(r, c)
