ZK-rollups and Optimistic rollups are both Layer 2 scaling solutions that aim to increase transaction throughput and speed by moving transactions off-chain¹². However, they differ in their transaction verification and dispute handling mechanisms¹².

Optimistic Rollups:

• They operate under the assumption that all transactions are valid by default unless proven otherwise¹².
• They use a fraud-proving scheme, with a dispute-resolution period known as a ‘challenge period’².
• They provide higher scalability and ease of implementation³.
• They can improve scalability by 10 to 100 times according to Ethereum¹.

ZK-Rollups:

• They use a complex piece of cryptography called a zero-knowledge proof to prove the transactions’ validity without knowing too much about the transactions’ specifics⁴.
• They offer enhanced security and privacy with slightly lower scalability³.
• ZK-rollups can save more gas than optimistic rollups, but they also have higher computational costs to generate their zero-knowledge proofs¹.

In conclusion, while ZK-rollups offer enhanced security and privacy, optimistic rollups provide higher scalability and ease of implementation³. The choice between the two would depend on the specific requirements of the use case.