No.
You are giving 100 Million over 3 to one of the Top SP in MLB. One that has a history of being a Top SP in MLB over a good number of seasons. That sounds pretty good compared to...
A) A SP in the open market that isn't either as Elite or doesn't have the consistent history as Zack
B) Hasn't been a top of the rotation SP
If you can sign Corbin (for example) to 20 million a year... ok. Doubt that happens. But he's hunting for 5 years or more. I'm done with Zack after 3.
3 years of Zack at 100 Million with the history of performance vs the market at minimum 25 million with at least 5 years if not more...
This isn't 2009, and Zack Greinke isn't one of the best SP in baseball. When he WAS the best SP in baseball in 2009, his FB averaged 94.1. In 2015 when he had his second best season, his FB averaged 92.5 MPH. Even last season when he was very good, his fastball averaged 91.0 MPH.
This past season, when he morphed into a 35-year old junkballer, his FB averaged 89.6 MPH to rank 51st out of 56 qualified SP in fastball velocity.
He's a very smart guy who knows how to pitch, and I'm not saying he won't be a valuable SP for the next 3 seasons. But he's not one of the top SP in MLB anymore.