Complex sentence: After becoming editor of "Asimov's", Dozois's fiction output dwindled, but he is now making a comeback, with his 2006 novelette "Counterfactual" winning the Sidewise Award for best alternate-history short story.
Split into simpler sentences: After becoming editor of "Asimov's", Dozois's fiction output dwindled. His 2006 novelette "Counterfactual" won the Sidewise Award for best alternate-history short story.