The text of the relevant part of the Equal Rights Amendment, currently batting its way around Congress:
Equality of rights under the law shall not be denied or abridged by the United States or by any state on account of sex.
And here is the end of Section 1 of the Fourteenth Amendment:
No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.
So what does the ERA guarantee that the Fourteenth Amendment hasn't already covered?