You can withstand more hits from zombies if you secure the Tuff 'Nuff perk. You'll have to visit the perk machine first, however. To do so, enter the Journey Into Space portion of the park (it's located to the left of the main teleporter, as you face it). Inside that area, make your way up the flight of stairs just beyond the Galaxy Journey portion. Look in a corner to the right to find the machine, and prepare to spend 2500 points to activate the valuable perk.