Since the 4351 doesn't allow importing/exporting sample clocks or start triggers these will only be synchronized in software. That being said, if you already have an example that runs the way you like on each individually it should be pretty easy to combine the two. Can you run both of the other VIs at the same time? If you can do this then I would just copy the entire block diagram from one example and paste it into the other. Then, if you want to start them as close to synchronously as possible you can wire the error wire from the 435X Acquisition Start/Stop VI into the start VI for the PCI 6070E. This will use data flow programming to ensure the devices start together within software error.
I hope this helps, and have a great weekend!