assuming you are able to land bolts and holy freeze hit before the smiter is on top of you, that's just 100% slow, with the 60%ias shield, he'll be at 9fpa which will still be able to trade 2 hits vs zon's impale and that's the best case scenario where your holy freeze + bolt hits him. Pally is also able to put some pts into holy freeze to have a higher lvl freeze than doom's lvl 12 freeze so the zon will also be frozen which makes her unable to impale essentially. bm vs bm zon has no chance
I never bothered with the slow bm in the matchup, its just the fact a pally can't smite/stomp/charge you without being repeatedly tagged by plague and every antidote he chugs is a full juv slot in belt. And it just reapplies nonstop and often just frames after his last antidote. All the zon has to do is kite run/walk vs smite/charge. And the pally has to make sure he's swapping aura/tele because trying to stomp with fanat off while slowed could lock him into a long smite animation, that's another
Now I always played damach or osama zon and almost never put on a doom swap so a 160/60 shield would be a big liability if I ever punish the approach / reset the gap and can pelt the pally with GA since he's going to be low block/dr, whereas a normal javazon or facing max dr/block you can just disregard bowside and stick pure java and have doom swap, sure.
But 35% slow from clegs/arachs isn't much and yes its trading into smites when you impale, so that's just 85% slow and if the pally isn't stacking ias its taking the 72 (normal), 97 (stacked) 121 (super stacked) down to a respective 13/10/8 fpa, compared to 6 fpa in all cases without slow and zon probably hitting 14 fpa without slow. And thats if you tag him with doom on approach.
or to quantify it more as a table
if he has 72/97/121% eias stacking (72% is the normal build breakpoint, anything above that is stack)
without slow they are all 6 FPA
with 35% slow from lightning bolt on clegs/arachs they become 8/7/6 FPA
with 85% slow from slow % + doom they become 13/10/8 FPA
with 135% slow from slow % + doom + impale they become 32/19/13 FPA and the pally is going to have to reset because he'll never land a hit when you just move away