Cyr., 4., 3.,19

οἶμαι ἔγωγε πολλοῖς μὲν ἀπορεῖν τῶν ἀνθρώποις ηὑρημένων ἀγαθῶν ὅπως δεῖ χρῆσθαι, πολλοῖς δὲ τῶν ἵπποις πεφυκότων ἡδέων πῶς αὐτῶν χρὴ ἀπολαύειν.
The commentary says that the first πολλοῖς depends on χρὴ, and the second is just pending, I think, however, that the first πολλοῖς depends on ἀπορεῖν and the second also on implied ἀπορεῖν.
NB Perseus has instead of the second πολλοῖς πολλῶν which is strange.

It doesn’t work to take πολλοῖς as dependent on ἀπορεῖν. ἀπορεῖν governs two indirect questions, ὅπως δεῖ χρῆσθαι + πῶς χρὴ ἀπολαύειν. The first πολλοῖς is governed by χρῆσθαι (always + dative). “I think the centaurs were at a loss as to how to properly use many of the things discovered by humans.” In the δέ clause, we expect another χρῆσθαι after πολλοῖς, but the construction switches and instead we get the genitive-governing ἀπολαύειν with an extra αὐτῶν. Another anacoluthon in the same speech. Marchant’s text here again smooths out the syntax, correcting it with πολλῶν for the second πολλοῖς and deleting αὐτῶν.

Again, I’d recommend using the critical apparatus in Marchant’s OCT as you work through these syntactical and textual issues.

so is this a prolepsis? I thought prolepsis would be either in N or Acc only.

It’s not prolepsis. In prolepsis, the “dislocated” word becomes the object of a matrix verb. Eg οὐκ οἶδα τὸν Κῦρον ὁποῖός τίς ἐστιν. (And there’s no requirement that prolepsis be restricted to nom or acc). In your passage it’s just hyperbaton, πολλοῖς being shifted to the beginning so as to bring out the antithesis πολλοῖς μὲν…πολλοῖς δέ. It’s totally regular. Do you see how this word order is better than, eg τοὺς ἱπποκενταύρους οἶμαι ἔγωγε ἀπορεῖν μὲν ὅπως δεῖ πολλοῖς τῶν ἀνθρώποις ηὑρημένων χρῆσθαι…?

yes i can see it now, thank you.