Question
My yard is sodded with zoysia sod. Over the past year i have experienced a major decay in my yard. My question is what can i do to help my yard recover, and if re-seeding zoysia over my sod is an option

Answer
Your biggest challenge is to correct the cause of the 'major decay', my friend.  Beyond that, there will be other solutions to fixing your Lawn; Zoysia is a disaster as an overseed.

I must ask you a few question.

Where are you writing from?  Your zipcode would pinpoint your Lawn's location and the likely climate, what we can expect from it.

Would you please elaborate on 'experienced a major decay'?  When did you notice the downhill trend?  How did things look before that?  What do you think caused it?

What is your Soil like?

How old is your Zoysia?  Any other Grass planted on your property?

What kind of mowing/maintenance do you actually do (or have someone else take care of)?  Any schedule?

rsvp for your solutions and options.  Thanks for writing.