But its that attack that is truly Zamazenta Vs best feature.
You do not want to send those cards in for grading
As mentioned before, being a good sport can benefit all players
While there's always a risk of fizzling, if the deck can untap with a Puresteel Paladin or Sram, Senior Edificer on Turn 2, there's a reasonable chance it will win the game that turn by casting a bunch of zero-mana equipment and using Mox Opal to produce mana for Retract, which bounces all of the zero-mana equipment and allows the Puresteel Combo player to draw through literally their entire deck before finishing the game with Grapeshot (with mana from multiple Mox Opals)
Thanks to flashback, this spell provides you with a casting of a powerful creature from your graveyard even if it happens to get milled into the graveyard along with them
My goal is not to fault you for playing those cards - I just feel the broader EDH format as a whole is becoming quite solved, in part by people turning to net-decking or using automatic online suggestion tools too often