In the light of BAT’s still ongoing pump (50%+ for the month), holders of other Coinbase listing candidate tokens are clamoring for their token to be next on the most famous crypto exchange. Even though it is seen as an outsider, ZEC actually stands more than a decent chance to beat the odds and be the next coin on Coinbase. This is why.
If we look it from Coinbase perspective, they are looking to cover as many different cryptocurrencies in terms of their use cases as possible.
Coinbase already has Bitcoin, BCH and LTC listes as regular payment coins. Ethereum and Ethereum Classic are dapp blockchains. Since couple of weeks ago, 0x and BAT which are both ETH tokens.
Adding ADA or XLM would just be adding another dapp platform, adding ZEC would be a first privacy coin on Coinbase.