The account activation fee is a one-time fee to register your account with zkSync. This fee only applies to your first zkSync transaction. On a deeper level, to be better suited for zero-knowledge proofs, zkSync accounts are defined over a different elliptic curve than Ethereum's. Activating your account generates and publishes a new private-public key pair over this curve associated with your Ethereum address. The registration process happens directly on the Ethereum smart contract and therefore it is an L1 transaction, so the activation fee is to pay the Ethereum miners and not zkSync validators. ERC-1271 compatible wallets (like Argent) increase this one-time fee because of higher interaction with the zkSync smart contract. This operation is cheaper if you are using a CREATE2 smart-contract-based wallet.