It is just an outdated usage to place the direct object pronoun in front of the first verb. Nobody does that any more.

In 21st French we would write:

• … on pourra le distinguer en six parties.

According to Grevisse (Le bon usage) this was frequent (but not systematic) until the 17th c. when there were two verbs, the second being in the infinitive (this is the case here). Examples they give:

D’autres aiment la vie je la dois haïr. (Corneille)

On nous veut attraper. (La Fontaine)

Grevisse gives some examples until the 19th c. The latest being found in writers who lived across the 19th and 20th centuries.