Place pistachio nuts in food processor; pulse until chopped. Add almonds, chocolate chips, ½ cup of sugar, cinnamon and lemon zest; pulse until nuts and chocolate are finely chopped and same size.
Unwrap fillo dough and cover with a damp paper towel.
Butter a 9-by-13-inch metal baking pan.
Butter and stack 10 sheets of fillo into the pan.
Sprinkle about 2 cups of the filling over the fillo. Gently shake the pan to even the layer of filling.
Butter and stack 4 more fillo sheets and place over the filling.
Sprinkle on another 2 cups of the filling.
Top with 4 more buttered and stacked sheets of fillo and 2 more cups of filling.
Butter and stack remaining sheets of fillo dough and place over the filling.
Brush top generously with butter.
Cut through all layers into about 3-inch squares and then cut each square into 2 triangles.
Bake for 25 minutes, then lower the oven temperature to 300° and bake for 50 minutes longer or until until golden brown.
Meanwhile, in medium saucepan, bring the water, espresso powder, lemon juice, honey and remaining 1 ½ cups of sugar to a boil. Reduce heat and simmer for 10 minutes.
Carefully pour the hot syrup evenly over the hot baklava and let stand for several hours or as long as overnight until completely cool.
Notes
For best results: defrost phyllo dough per package instructions and keep phyllo covered with a damp cloth or plastic wrap to prevent it from drying out.