Solution
Though a DAQmx task can bundle multiple channels together, it is usually restricted to accessing only one hardware device (with the exception being Compact DAQ, S Series, X Series, and DSA modules). If you try to combine multiple devices into one task, as shown below, you will receive this error because each device will have its own sample clock and a task can only time off of one sample clock.
Instead you should use a separate DAQmx task for each device, as shown below.
The excluded modules allow such a setup because S Series, X Series, and DSA modules support channel expansion for analog input (see related KnowledgeBase linked below), and Compact DAQ chassis can use a single sample clock for all modules they contain.