The TZMaps chart subscription for TZ iBoat is a good bargain and by far the cheapest way to get access to very detailed bathymetric charts. I have not tried it but I think you may still be able to do a local synchronization between the iPad and a TZT 2 and transfer waypoints created on the iPad to the TZT2. Put the TZT2 into "Local Network/Access Point" mode to create a local Wi-Fi network. Then join that network with the iPad and run the TZ iBoat app.
Next time I am at my small boat that has the TZT2 displays, I will try it and see if the waypoints in TZ iBoat get transferred to the TZT2. I am reasonably certain that when Furuno/Time Zero disabled the synchronization, it was only for the TZ iCloud over the internet, not local synchronization.