I've started reading Johann Schweighäuser's 1822 translation into Latin of Herodotus' Histories, and already the first sentence is giving me some trouble.
The Greek, which I can puzzle my way through just about half of, reads
Ἡροδότου Ἁλικαρνησσέος ἱστορίης ἀπόδεξις ἥδε, ὡς μήτε τὰ γενόμενα ἐξ ἀνθρώπων τῷ χρόνῳ ἐξίτηλα γένηται, μήτε ἔργα μεγάλα τε καὶ θωμαστά, τὰ μὲν Ἕλλησι τὰ δὲ βαρβάροισι ἀποδεχθέντα, ἀκλεᾶ γένηται, τά τε ἄλλα καὶ δι᾽ ἣν αἰτίην ἐπολέμησαν ἀλλήλοισι.
One English translation of the passage reads
These are the researches of Herodotus of Halicarnassus, which he publishes in the hope of thereby preserving from decay the remembrance of what men have done, and of preventing the great and wonderful actions of the Greeks and the Barbarians from losing their due meed of glory; and withal to put on record what were their grounds of feuds.
Another, more recent translation (Tom Holland's) reads
Herodotus, from Halicarnassus, here displays his enquiries, that human achievement may be spared the ravages of time, and that everything great and astounding, and all the glory of those exploits which served to display Greeks and barbarians alike to such effect, be kept alive—and additionally, and most importantly, to give the reason they went to war.
Schweighäuser's version reads as follows:
Herodotus Halicarnasseus, quæ quum cæteris de rebus, tum de caussa bellorum Græcos inter Barbarosque gestorum, perquirendo cognovit, ea his libris consignata in publicum edit; ne, quæ ab hominibus gesta sunt, progressu temporis oblivione deleantur, neve præclara mirabiliaque facta, quæ vel a Græcis edita sunt vel a Barbaris, sua laude fraudentur.
My fairly literal translation of the Latin is
Herodotus of Halicarnassus publishes the things (set down in these books) which he recognized in researching as much into the cause of the wars waged between the Greeks and the barbarians as into other matters, lest the acts of men be wiped out into oblivion by the passage of time, or lest the wondrous and most famous deeds performed by the Greeks or the barbarians be cheated of their praise.
I'm having trouble with "quæ quum cæteris de rebus, tum de caussa," for two reasons:
1) My understanding is that the cum X, tum Y generally means "as much Y as X." But there's nothing like that in the English or, as far as I can tell, in the Greek.
2) There's nothing like "into other matters" in the English or, as far as I can tell, in the Greek.
What's going on with this phrase? (My Greek is very rudimentary, so if there's a discussion of the Greek in your answer, I'd love it if you transferred the explanation to the English.)