Complex sentence: GN-z11 is 25 times smaller than the Milky Way, has 1% of the Milky Way galaxy's mass in stars, and is forming stars at a rate about 20 times faster than the Milky Way galaxy does today.
Split into simpler sentences: GN-z11 is 25 times smaller than the Milky Way and has 1% of the Milky Way galaxy's mass in stars. It is forming stars at a rate about 20 times faster than the Milky Way galaxy does today.