Well, the best approach to this would be to have separate RequestQueue instances for the separate crawlers and to add requests directly to the queue of the right crawler in your request handlers. There are however some challenges:

• As of now, you need to make named queues, because Request.open() will always resolve to the same unnamed queue. This may or may not be a problem if you're running on Apify. Locally, you'll probably need to purge the named queues manually before each run.
• Just waiting for both crawlers using something like await asyncio.gather(crawler_1.run(), crawler_2.run()) also won't work right off the bat - I assume that only one of your crawlers will have some start urls and the other one will exit immediately. In JS version, we have a keepAlive option, but that is not available in crawlee-python yet.

We are aware of this shortcoming though, and we'd like to enable running multiple interconnected crawlers in the future.