What brand and model of valve did he install? He would have to go some to convince you that they are equivalent to Champ brass, but there are others.

DId he provide you with a system design drawing with his quote?

There is a big difference between 9 valves/65 heads, and 5 valve/45 heads. So, you need to be convinced that the NEW design has adequate coverage, overlap, GPM sized to pipe, water velocity not excessive. All these things will haunt you FOREVER if they are not correct.

So, if it turns out that the new design is adequate and materials are satisfactory, it seems at least that an adjustment is in order. Many installers base their quote on something in the range of $250 to $450 per zone; so 5 zones instead of 9 is a lot of money.

Are you dealing with a real landscape contractor or a guy with a couple of shovels on the back of a truck who say "I do these all the time". ?