Zhulodok, Void Gorger

Due to a 2021 rules change to cascade, not only do you stop exiling cards if you exile a nonland card with lesser mana value than the spell with cascade, but the resulting spell you cast must also have lesser mana value. Previously, in cases where a card's mana value differed from the resulting spell, such as with some modal double-faced cards or cards with an Adventure, you could cast a spell with a higher mana value than the exiled card.

Once you announce that you're casting a spell, players can't take action until you've finished casting it. Causing Zhulodok, Void Gorger to leave the battlefield after you've cast a colorless spell from your hand with mana value 7 or greater won't stop that spell's cascade abilities from resolving.

If you cast a card "without paying its mana cost," you can't choose to cast it for any alternative costs. You can, however, pay additional costs. If the card has any mandatory additional costs, you must pay those to cast the card.