@WindUp951
I think you are overlooking the essentials of both Special Abilities.
The Pea Gatling ability is intended to be a huge threat to any Zombie who gets in its sights and the intention is for it to be highly damaging. This rapid fire, high damage output is received by trading off your mobility and becoming a completely stationary target until you uproot. If you root in a bad spot and fire even a single shot when you uproot to get a better vantage point the remainder of the ability is wasted and it goes directly into Cooldown. Because the ability is based on your available ammo, so missed shots are really wasteful, and because you are immobile and easily vanquished the ability was granted a short cooldown time.
The default Z-Mech is also intended to be a huge threat to the Plants and the intention here is clear to be able to dish out and receive high amounts of damage. Unlike the Pea Gatling the Z-Mech retains full mobility and is able to carry it's firepower to various areas of the battlefield. Rather than having it's duration decided by it's ammunition count it is instead based on a fuel source which constantly depletes and it's ammunition functions independently of its fuel supply. It carries a primary weapon which doesn't need reloading so with burst control you can avoid the overheat penalty and fire an unlimited amount of ammunition and this is backed up by Missle Madness which launches a barrage of twenty missiles, each of which having a large amount of Splash damage and it possesses a Stomp attack which does high damage and has a large area of effect. If this wasn't enough the Imp can also eject intentionally before the Mechs Health is depleted and trigger a high damage self-destruct. Because of all these capabilities an the fact that they can be carried anywhere on the battlefield it has a longer Cooldown than the Pea Gatling.
When I play on the Zombie team I stay aware of the number of Pea Shooters on the Plant team and I watch for when they initiate their Pea Gatling attack because they are a prime target since they can only just sit there and most Pea Shooter Players will try to locate you for a counter-attack instead of Uprooting to seek cover and that tends to make them an easy vanquish; I either take them out from a distance or from the flank because they are sitting ducks if their attention isn't on you and on the occasion when I stumble into their sights I do my best to not stand there and take every shot that they want to send my way; sometimes I get to cover and sometimes I don't but I recognize the ability for what it is and I don't whine about it when I get mowed down. I have very few Z-Mechs destroyed by Pea Gatling because I don't call it down right in front of the Plants and I don't rampage around with it as if one isn't going to be set up right around the corner waiting for me.
You should also try to avoid ad hominem attacks when you're trying to defend your position in a conversation/ debate such as this. The playing style, relative level of skill, Player rank, number of unlocked characters, etc, are all irrelevant when it comes to the position which they are maintaining.
