Zucoins is a truth network and not a consensus network. Therefore, transaction validation is performed by finding the truth of both peers transacting.
Consensus networks can be compromised when enough people decide to change their opinion on what transactions are considered acceptable or not. Effectively, transaction success relies on a vote controlled by an increasingly centralised group of network validators.
Only the most recent transactions are cached across the SplitChain network. This is done so that others can find the truth they need to transact reliably with another user, while keeping the network fast and lightweight.