Is the mass a re-crucifying of Jesus, or is it making what Jesus did on the cross present at the Mass?
It’s the re-presentation, in an unbloody manner, of the Son’s eternal self-sacrifice to the Father.
This is one of the areas in Catholic theology where one must be careful in one’s terminology. You can read more here:
What James said.
Christ’s sacrifice was done once for all and at the Mass we are present at His sacrifice which is both within time and outside of time. We’re talking about the Son of God here, everything is possible.