Welcome to FlyerTalk ottflyer!

I think you're not leaving enough time for the transfer. Even if your flight from Venice arrives on time, there's no guarantee that you'll have a gate, and a bus gate will take a few minutes. Lines for immigration can be long, even on the fast track. Then you'll need some time to store your luggage. You will have to walk to the domestic terminal (it's not far, but it will take a few minutes), and go through security on your way to the gate. If everything goes well, two hours should be plenty, but things don't always go well. Do you have a backup plan in case you miss the Izmir flight? Are your Pegasus tickets changeable?

Personally, I would leave more time when combining two separate tickets, especially if missing the second flight would be a major hassle.

Shuly