  We find an asymptotic formula for the number of primitive vectors
$(z_1,\ldots,z_4)\in (\mathbb{Z}_{\neq 0})^4$ such that $z_1,\ldots, z_4$ are
all squareful and bounded by $B$, and $z_1+\cdots + z_4 = 0$. Our result agrees
in the power of $B$ and $\log B$ with the Campana-Manin conjecture of Pieropan,
Smeets, Tanimoto and V\'{a}rilly-Alvarado.
