The term "ekporeusthai" is understood by the Greek Fathers, and notably the Cappadocian Fathers (whose theology shaped the Second Ecumenical Council), to refer to the Spirit proceeding from the Father. "Proienai" is vaguely understood by them, but more strictly understood by Maximus the Confessor and Cyril of Alexandria, to refer to the Spirit's flowing forth, or progression, from the Father and the Son.
"Procedere" probably is a better translation of "proienai" than of "ekporeusthai," but the Latin defenders of the filioque have historically almost always included "ekporeusthai" and "proienai" both under "procedere," especially at the Council of Florence.
Now, with that in mind…
Christ Himself taught procession from the Father alone in John 15:26. He would have said "the Holy Spirit proceeding from us" otherwise.
Dionysius and Athanasius both call the Father "the one source of the pre-essential godhead . . . [and] the only source of the Divinity."
Gregory Nazianzus says that "everything the Father has belongs to the Son with the exception of causality."
The Third Ecumenical Council had approved portions of the Nestorian creed presented by the priest Charisius, including the statement that "the Holy Spirit is not the Son, neither does he take his existence through the Son."
Theodoret accused Cyril of Alexandria of stating that "the Spirit receives his existence from the Son or through the Son," but Cyril denied this, agreeing with Theodoret that this is a heretical thought.
The Latins at Florence used corrupted sources to prove that the Son is cause of the Holy Spirit. The Latin excerpts of Basil's Adversus Eunomium were co-mingled with parts of Eunomius's own work, and the Latins cited explicitly Macedonian parts of the text in defense of the filioque (for instance, that the Spirit is "third in order and dignity").
The Fathers of the Second Ecumenical Council were led by the Holy Spirit to only state that the Holy Spirit proceeds from the Father, with nothing further added, and the Third Ecumenical Council forbade any additions to the Creed, which was understood by the later Greeks to mean any sort of addition, and to refer to the creed of Nicene-Constantinople - calling it the Nicene Creed to honor the Fathers of the first council, just as later ecumenical councils would.
Cyril of Alexandria, who presided over at Ephesus, said: "We prohibit any changes whatever in the Creed of Faith drawn up by the holy Nicene Fathers. We do not allow ourselves or any one else to change or ormit one word or syllabe in that Creed."
The Fathers of the Fourth Ecumenical Council said that the Nicene-Constantinopolitan Creed "is sufficient for the full knowledge of the truth, for it contains in itself the full doctrine of the Father, the Son, and the Holy Spirit."
Knowing all this, one can only say that the Holy Spirit proceeds (hypostatic origin) from the Father alone, and the Latin "proceeds from the Father and the Son" is not equivalent to the Greek "proceeds from the Father through the Son" but rather to the Greek "progresses/flows forth from the Father and the Son," denoting not hypostatic origin but the eternal sending forth of the Spirit by the common will of the Father and the Son.
The Holy Spirit proceeds from the Father to rest upon the Son, rather than proceeding from the Father and the Son. Other expressions are that the Spirit is manifested through the Son, or shines forth from the Son, and one may say well that the Holy Spirit finds existence from the Father (proceeds from the Father) and continues existence through the Son by Whom He is sent (proceeds through the Son, or flows forth from the Son). To say that the Spirit finds existence from the Son is erroneous. To say the Holy Spirit proceeds (ekporeusthai) from the Father and the Son is to say that, at the Theophany, the Father did not simply anoint the Son - the Son anointed Himself as well, or worse, anointed the Father back.
But anyway. Let's recognize that procedere = proienai, that the creed wasn't well translated into Latin, that Latin sucks overall, and move on.