Put on the hub bolts and torque them back up. By pulling the hub and housing together, this can re-align the mating surfaces, and break apart any rust bonding. When loosening the bolts, do so in a cross pattern sequence; and only a little at a time (as you would when tightening). This allows the pressure to come off evenly, on all four bolts; leaving less chance that the hub is skewed within the housing (which otherwise, will cause binding).
Heat (propane, Mapp torch), on flange and where hub inserts into housing (being careful of brake lines, cv boots, wheel speed sensor etc).
Can follow up with a freeze penetrant (wurth - roost off ice, or Loctite version). Then re-heat.
Air hammer with flat face bit; to vibrate and shock loose, any surfaces that are bound together (between hub and housing).
Hub/bearing puller, if you have (or can borrow), one. It may initially just press the shaft from the hub; but when the drive shaft compresses, there may still be enough length to pull the hub from housing. Or at least the total friction on the hub will be reduced, so other methods are more effective on hub and housing.