If my opponent used Zoroark's "Foul Play" attack their previous turn, could I play Guzma to bring up a benched Pokemon and have Sudowoodo's "Watch and Learn" attack use "Foul Play" to copy one of the new Defending Pokemon's attcks?
Yep, that works.
Source: TPCi Rules Team (2018-03-01)

Relevant cards

Note: All applicable cards may not be listed below.
XY9_67