Getting Access to Summon Monster

[Zombulian]

Argue that knowledge arcane gives you knowledge of summon monster. And that spellcraft teaches you how it is cast Alternatively add a rank in knowledge:summon monster.

Hope this helps!

I know you’re joking but in all honesty, how meaningful is the phrase “must know X spell” when most other instances of casting requirements are phrased “must be able to cast X spell” or “must have X spell known”?

It may very well be possible that simply being aware of Summon Monster spells and capable of casting 4th level spells qualifies you for NDB.