A voltage divider is not a voltage regulator.
The zener diode will "clamp" the same voltaqe constant across it's terminals (assuming there's enough in the supply voltage).
The voltage divider's voltage will vary proportionally to the supply voltage.
I believe one should have a stock of 7805, 7812, 7905, 7912, 317s, 337s and 3.3 volt regulators in their pile of parts. You can get these parts very cheap in TO-92, or TO-220 packages.