Peter said the law was an unbearable yoke for Israel, so it doesn't matter if Jews in Jerusalem were zealous for the law. That was their choice because that was what they were acculturated to. It was by no means a requirement of the gospel.
btw the gospel of the kingdom pertains to the kingdom of God/heaven into which gentiles became citizens via faith, just as the Jews were. There is no difference
Now therefore why tempt ye God, to put a yoke upon the neck of the disciples, which neither our fathers nor we were able to bear? But we believe that through the grace of the Lord Jesus Christ we shall be saved, even as they. Acts 15:10-11
