Does Grimgore Ironhide also remove the support cards of the active player as well as the opponent? If yes, then what's the strategy to play this card, wait until your support cards are gone? I understand this only applies to the matching zones to the zone of play.

Limit one Hero per zone. Forced: After this unit enters play, destroy all support cards and developments in each player 's corresponding zone.

Each player means each player.

You also can play no dev in the zone where you want to play Iron.

You also can state that opponent dev give him a better advantage than yours ....

Usually after Grimgore destroys everything you'll be in a better positition than your opponent especially when he plays something that's either centered around heavy kingdom or battlefield developments. You can also shut down his questzone when he is low on cards.

OK thanks I can see how it works now.