Domain Zoo is an aggressive, low-curve deck that relies on efficient threats like Ragavan and Territorial Kavu plus cheap interaction such as Lightning Bolt and Consign to Memory, so having your own Consign to Memory helps counter colorless spells like Scion of Draco or key triggered abilities and disrupt their tempo plan. Force of Negation lets you counter a key noncreature spell like Leyline Binding for free on their turn, protecting your board development from their removal. Basim and Bilbo are fragile 2/2s that trade poorly into their efficient removal suite (Lightning Bolt, Leyline Binding) and don't survive combat with Ragavan or Territorial Kavu, so they're cut in favor of proactive countermagic that protects your engine pieces and stops their key spells.