I couldn't understand what is the use of second parameter. Your work can be done with one parameter.
Create your fetch with a parameter in it (say dataset1). Now create a fetchXML (say dataset2) that fetches you account id.
For the parameter from dataset1, set default value as "Get values from Query" and pass "account id " from dataset2 to it. That's it your job is done.
Note: Remember to select Forms for related record types in
Display In area and Account in Related Record Types area.
Jugal Kishore Dandamudi.