Upvote:2
(Answering having read the original post prior to the edit)
a. No marriage can occur until their prior marriage that ended in divorce is examined by the Church and a decree of nullity issued (i.e. in the eyes of the Church, that marriage never existed to begin with).
b. Once that decree has been issued, the requirements for a mixed marriage must be met for there to be a valid marriage in the Catholic Church.
Endnote
My answer to Do divorced non-Catholics need an annulment to marry in the Catholic Church? stated:
Thus the Church recognizes the marriages of non-Catholics as well and considers them valid until proven otherwise.