Always use 194mm for low flange hubs with a X3 pattern. 184 - 186mm for High flange hubs with a X3 pattern
If you want to use a X4 pattern, you will need around 196mm dude but you can stretch them easily if you have 15mm nipples
I would agree if you were lacing Araya 7X style rims, but a Z-rim has a raised centre so you will need shorter spokes.
I've got a log of rim/hub/nipple/spokes sizes and lengths that i've been keeping as i have been building wheels and as said i've not built that combo yet so i can't say for sure.
I have built...
z-rim/lf 3x=181's,
z-rim/sf 3x=184's,
z-rim/bullseye 3x=184's,
z-rim/phil wood 3x=184's,
7x/lf 3x=184's,
7x/sf 4x=194's,
7x/bullseye 4x=194's,
20x1-3/8"/lf 2x=194's
So i think 196's will be way too long