Yes, paddles are a fantastic tool. There are two ways to accomodate this:
1. Perform a swim test using paddles. You’ll then have two sets of zones: with and without paddles. When you don’t use paddles, your Zone 2 is up to 1:40 per 100, when you do use paddles, your Zone 2 is up to 1:35 per 100 (for example). This carries some risk, as Zone 3 with paddles is for advanced swimmers, and if you use huge paddles I would not go more than 100 meters at a time with Zone 3.
2. Use perceived effort when using using paddles. You sort of know what Zone 1-5 feels like anyway when swimming, so just slip into perceived effort and go by what feels like the correct zone.
Zone 2 is the perfect zone for paddles. You can safely and effectively use up to 50% of your total Zone 2 time with paddles, and up to 25% of your total swim time.