Well, with Zone it all depends on your lines. Considering Zone has draw consistency, the faster you get Zone out the faster you pull an Eel out. I'm assuming you run Sage's and Junipers? With draw discard, some junk arm and a Super Rod possibly as well?
If you have a lot of draw-discard run 4/3 to cut back on the concern. (Psst, between you and me, if you're going to run four Tynamo, run the Tynamo with free retreat. It's really handy for abusing other Eel on your bench and when your active is KO'd, you can place out Tyamo, abuse eel's ability and retreat freely as needed. A lot of people don't catch on, but that's why I'm informing you.) :wink: 40 HP isn't as big of a deal vs 30 HP. The only things I can really think of are Tyrogue and Crobat. Otherwise, if something is going to bench snipe the Tynamo for a prize or catcher KO it, they'll KO it regardless of the 10 HP difference anyway. It's too low to matter, especially with that fighting weakness.
I can only speak from a Lanturn / Raichu perspective. But I run 4/4 in Raichu and run into some consistency problems. I run 3/3 in my Lanturn and I don't necessarily lack consistency at all.