Say Sky Field is in play and I have 8 Benched Pokemon, then I use Marshadow's "Resetting Hole" Ability. Do I discard Marshadow first and then discard down to 5 Benched Pokemon for the removal of Sky Field, or do I discard down to 5 Benched Pokemon first and then discard Marshadow?

The player who owns Marshadow can choose the order of discarding Benched Pokemon, either before or after the removal of Sky Field.

Relevant cards

SM10_81