Good morning. I have a Craftsman Zero Turn with a Kohler Z6000 engine and I'm trying to replace the muffler, but I can't get a tool in to remove and replace the bolts that hold the exhaust pipes to the engine. Does anyone have any tips I can use? 
Thank you.

Your bolt head is very likely a torx head, or possibly an allan key head (round on the outside).
 
https://search.yahoo.com/search?fr=mcafee&type=E210US1498G0&p=torx 
 
As space in there is very limited, for a torx, 3/8 drive socket, one of those cheap, multi size, foldable
tools should work for you, IE:
 
https://www.amazon.com/torx-multitool/s?k=torx+multitool 
 
Look at your bolt head first before purchasing a torx tool, or 
allan head tool.
 
.

Thanks for your replies. Yes, they are torx bolts and in an extremely tight space. Are you suggesting an allen wrench?

No, I was stating the multi TORX tool would likely get in there much easier.
 
https://www.amazon.com/torx-multitool/s?k=torx+multitool