The headword as transmitted is r(a|die/steron (whereas the quotation has feminine r(a|dieste/ran); seemingly, then, the headword has been extracted from somewhere else.
The Attic comparative of r(a/|dios is r(a/|wn. See e.g. rho 40.
[1] Polybius 11.1.1, on events of 207 BCE; cf. Livy 27.39.6. (Than what this was "easier and quicker" is left unstated: the Loeb translator, W.R.Paton, understands "than that of Hannibal had been"; Walbank in his commentary ad loc. prefers the vaguer "than expected".)