Catalysis of the reaction: GDP-2,4-diacetamido-2,4,6-trideoxy-alpha-D-glucopyranose + H2O <=> 2,4-diacetamido-2,4,6-trideoxy-alpha-D-mannopyranose + GDP + H+.
Statements about GDP-2,4-Diacetamido-2,4,6-Trideoxy-Alpha-D-Glucopyranose Hydrolase/2-Epimerase Activity