Step 1: The solubility product constant \( \text{K}_{sp} \) for zirconium phosphate is given by the relation:
\[
\text{Zr}_3(PO_4)_4 \rightleftharpoons 3\text{Zr}^{4+} + 4\text{PO}_4^{3-}
\]
Step 2: The molar solubility \( s \) of zirconium phosphate will lead to the following concentration expressions:
\[
\text{[Zr}^{4+}\text{]} = 3s, \quad \text{[PO}_4^{3-}\text{]} = 4s
\]
Step 3: The expression for \( \text{K}_{sp} \) is:
\[
\text{K}_{sp} = [\text{Zr}^{4+}]^3 [\text{PO}_4^{3-}]^4 = (3s)^3 (4s)^4
\]
Step 4: Simplifying this expression:
\[
\text{K}_{sp} = 27s^3 \cdot 256s^4 = 6912s^7
\]
Step 5: Thus, the molar solubility expression is \( \text{K}_{sp} = 6912s^7 \), which corresponds to option (1).