Sharp zero forcing numbers for the generalized Petersen graphs $P(n,3)$ and $P(n,4)$

We prove that $Z(P(n,3))=8$ for every $n\ge13$ and $Z(P(n,4))=10$ for every $n\ge18$, with both stabilization thresholds sharp, and give the exact values for all smaller admissible $n$. The first equality proves Krishnan's Conjecture 5; his Proposition 4 supplies its upper bound. The lower bounds us