Mobs will not attempt to pathfind around powder snow like they do other hazards. They will just walk right into it, and become trapped as a result.

How to replicate:

Place two blocks that are about 3-4 blocks apart, with nothing but empty void surrounding them

-Spawn a Zoglin on one

-Spawn any mob that isn't a creeper or another Zoglin on the other

-Connect the two using a bridge of powder snow

(Note: the Zoglin is just an example, this works with any mob that is hostile towards another mob)

Expected result:

The Zoglin simply stares at it's target, as it has no safe path to reach it.

Actual result:

The Zoglin walks right over the powder snow in an attempt to reach it's target, then proceeds to fall through it and into the void.