The balanced chemical equation for this reaction series is:

Zn + 2HCl → ZnCl2 + H2
ZnCl2 + 2NaOH → Zn$OH$2 + 2NaCl
Zn$OH$2 + 3H3PO4 → Zn3$PO4$2 + 6H2O

Overall reaction:

Zn + 2HCl + 2NaOH + 2H3PO4 → Zn3$PO4$2 + 2NaCl + 5H2O