your son is suffering from acute dysentery
for which he has been rightly prescribed antibiotic & zinc .There is no need to give zinc more than 20 mg /day.
If his vomitings are stopped & as long as he is able to retain ORS solution by mouth iv fluids can be avoided.
He needs about 200 ml of ORS for each loose stool
or vomit .
has no role in acute dysentery & can probably be stopped.
For tummy pain & fever both simple crocin syp 15 mg/kg/dose every 4-6 hrs is enough.
does not improve in 48 hrs pls get your son’s stool checked for microscopy to rule out amoebiasis
I hope I have clarified your queries.