How to join / synchronize process instances?

The “GetData” workflow will collect data from two servers every day, from server A at 9am, server B at 10am. “ServerName” is the only parameter the workflow requires.

Now there is a “ProcessData” task which is supposed to run as soon as both downloads succeeded.

I guess this is a rather basic requirement, but I have no idea how to model this. Can someone tip me into the right direction? I tried stuff like parallel execution of subprocesses but cannot seem to get it halfway right.