The biggest threat to users of cryptocurrency, including Zcash, is having the device where they store their private keys hacked and those keys stolen. Think about the grandma who clicks on misleading popup ads.
Paper wallets are one solution, but it is a pain in the neck to send funds from a paper wallet.
Hardware wallets are another, but not all users are going to buy a new piece of hardware. And then there is figuring out how to use it-- most are far from intuitive. Think about the grandma who can just about use an iPad but nothing more complicated than that.
And yet Zcash, and for that matter all cryptocurrencies, are doomed to failure unless that grandma can store it securely and use it to transact. See my other thread about that.
The best solution to the problem that I have seen is this pair of apps for Android and-- yes! iPad, the AirGap Vault and AirGap Wallet, https://airgap.it/ . I have no connection to this project except as a satisfied user, but I think it checks all the boxes: security, convenience, and low cost.
The way it works is, your private keys stay on an air-gapped device, which runs the Vault app. Once you have the app loaded, you never need to connect it to a network again. You transact using a device which is on the network, running the Wallet app. Data is passed between the two using one device’s camera to scan QR codes displayed on the other device. (In a pinch, of course, you can run the two apps on one device-- but then you lose the air-gap security.) The cost is low because at this point everyone has an old phone, tablet, or iPad hanging around.
There’s more on their website or their github– to their credit, everything is open source and the builds are even reproducible.
The app pair supports a number of cryptocurrencies, and I think Zcash should be one of them. The main developer, Andreas Gassmann, writes that the main issue with supporting more cryptocurrencies are time and funding. There’s nothing we can do to give him more time, but I think a community grant should give him the funding. Maybe once shielded-by-default goes live? It would be a shame to only have support for transparent addresses.