Complex sentence: Shamli was declared as a district in September 2011 and was named as prabuddh nagar by Mayawati, who was CM of UP at that time, but in July 2012 Shamli got its old name by Akhilesh Yadav who became CM of UP in 2012.
Split into simpler sentences: Shamli was declared as a district in September 2011 and was named as prabuddh nagar by Mayawati, who was CM of UP at that time. In July 2012, Shamli got its old name by Akhilesh Yadav, who became CM of UP in 2012.