Domain Zoo doesn't have blue-heavy spells outside Stubborn Denial and Spell Pierce, so Mystical Dispute costs the full {2}{U} but is still useful to protect your combo turn from a counterspell or to answer a key Leyline Binding. Into the Flood Maw bounces their Scion of Draco or Territorial Kavu to buy time against their aggressive curve. Nature's Claim has very few targets since they run almost no artifacts or enchantments (only Leyline of the Guildpact as an enchantment). Veil of Summer is weak here too since their interaction is red-based (Lightning Bolt, Tribal Flames) rather than blue/black, so we prioritize the more broadly useful Dispute and bounce spell.