If Player A uses Ghoulcaller Gisa to sacrifice Walking Corpse for 2 2/2 zombie tokens is there a way to stack triggers to have the 2/2 zombies obtain the +1/+1 counter from Mazirek, Kraul Death Priest?
No, because you only have 1 trigger (Mazirek's). Gisa's ability is an activated ability so it is put onto the stack and then costs are paid. Then, when costs are paid, it triggers Mazirek, but Gisa's ability is already on the stack waiting to resolve. Mazirek's ability will go on the stack above Gisa's and will resolved before you get the new Zombies.
If Player A uses Ghoulcaller Gisa to sacrifice Walking Corpse for 2 2/2 zombie tokens is there a way to stack triggers to have the 2/2 zombies obtain the +1/+1 counter from Mazirek, Kraul Death Priest?