Firstly, this spell?
https://www.wowhead.com/spell=132578...o-the-black-ox According to Wowhead the name of the spell is actually "Invoke Niuzao, the Black Ox".
Second, I do not think there is a way to cast spells by ID with macros as there is with items. You may need to use a modifier or right-click for the second spell.
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"You'd be surprised how many people violate this simple principle every day of their lives and try to fit square pegs into round holes, ignoring the clear reality that Things Are As They Are." -Benjamin Hoff,
The Tao of Pooh