Pokémon Card Lab is killing me here. Porygon-Z is my favorite Pokémon, but it keeps getting these uncompetitive cards. And this latest one... wow, does it suck.
That Ability might seem interesting at first, but there are two major flaws I can immediately see with it. For one, it sends the devolved cards right back to the opponent's hand. That means they can just play 'em right back down after your turn, so you'd have to either put enough damage on something before devolving it so it dies right there or be ready to follow up with hand disruption (something like N) in order to get anything out of it (even then, the latter might fail).
This is exacerbated by the second major flaw: it's a Stage 2 Pokémon. This forces you to either use a Rare Candy or, if you want to use something like Devolution Spray, wait another turn by playing the Stage 1 Porygon2 first. Both of these are a major hassle and a strain on precious deck space, and if you ask me, that Ability's just not worth it.
Do I even need to go into how worthless that attack is? Just read it yourself and let it be its own damning testament.
PCL, would it kill you to make this Pokémon playable for once?