Iago said, "Probal to thinking and indeed the course, To win the Moor again."
This is Iago doing his best to win the Moor back. He's trying his best to make the Moor like him better than Cassius because Iago is jealous of him because the Moor made him his lieutenant. He's making Cassius look very bad
Roderigo said, "...But one that fills up the cry."
This is a conversation between Roderigo telling Iago that hes hurt from getting whooped by Cassio but Iago said that their planned work and they got the best of Cassio. They did this because Iago is jealous of Cassio's job.
Iago said, And thou, by that small hurt, hath cashiered Cassio."