The Scotsman cruised through the first two sets, but lost the third in a tie-break before resuming control to book a place in the quarter-finals.
"He's a fun player to watch but not to play against," BBC Sport quotes Murray as saying.
"He made it very tricky for me, he's very unorthodox. You want to, if you can, close these matches out when you have the opportunity.
"I think I had three or four match points on my own serve. I tried to stay focused at the beginning of the fourth set, got an early break and that helped."