Sync with electrical wall outlet
I have two ac souces (sic) one being the electrical wall outlet and the othee (sic) being an inverter that will go to zero volts, ...


I don't know what "will go to zero volts" means but read on ...


  ... and both at 60hz. 


That will be 60 Hz nominal. The mains frequency will drift and so will the inverter.

How do I sync the inverter to the wall outlet?

If it doesn't have sync built in then you can't. The inverter will quickly be a permanent 0 V output.

Even if you could there is more to it than just connecting them up. Protection is required to prevent the inverter feeding out to the grid in the event of a power cut. You would be trying to power the neighbourhood and risk electricuting a lineman trying to repair a line.

Don't try it.