Well you know that all sides of a rhombus are equal menaing GD AND FE HAVE THE SAME LENGTH
And you know that two sets of angles are equal because the rhombus is a parallelogram meaning angles GDH is equal to angle HFE and vise versa with angles HGD And angle FEH ( z- pattern) - same angles also mean they are the same in length
Lastly angles DHG and angles FGE are the same because the are opposite angles
Therefore the two triangles a re congruent