Yes, sometimes one pitcher will get far less run support than another on the same team, or far more. The quality of the other team’s pitchers can be a factor but there is not always a discernible reason for these kinds of things over the course of a whole year. Sometimes pitchers just don’t have much luck with run support. Statistics like wins and losses don’t take that into account, which is one reason people are paying more attention to other measurements that focus on the stuff the pitcher can control. Zimmermann has an unimpressive 5-6 record this year, but yes, the other stats say he’s been much better than that.
Zimmermann has 1.12 walks and hits per inning pitched, 74 strikeouts and 22 walks this season. His ERA+, which takes his ERA, adjusts for the various ballparks he’s pitched in, and compares it to the rest of the league, is a very good of 151. Strasburg is 9-4 with a WHIP of 1.10, 128 Ks and 28 walks and an ERA+ of 140. Gonzalez is 12-3 with a WHIP of 1.11, 118 strikeouts and 42 strikeouts and a 135 ERA+. So in terms of those stats, yes, he’s at about the same level as the other two pitchers. On the other hand they strike out far more hitters than Zimmermann does and I think that has to work in their favor- especially Strasburg, who leads the league in Ks. Strasburg has walked about the same number of hitters as Zimmermann while striking out almost twice as many. Zimmermann strikes out 3.3 batters for each walk and Gonzalez is at 2.8, which is a less favorable radio- but still, he strikes out a lot more batters.