Is there any reason I can't charge other protected cells in my Thrunite TC12?

I am relatively new to Li-ion batteries but have been reading on different flashlight forums for years. Resisted going over to Li-ion batteries for several years and finally bought a TC12 in spring/early summer. I really like it and I like being able to charge the cell in the light. I don't have a separate charger and it the Thrunite is my only 18650 light. Question is, can I charge other protected cells in my tc12? I don't see why not. Cell I am wanting to charge is a Zebralight ZL634.

Don’t see why you couldn’t charge it as long as it’s an 18650, buy why not buy a charger, something like this

Nitecore, xtar, Opus, all make quality chargers and they arent expensive

Exatly .

You can find even cheaper chargers if you wish , like liitokala lii-100 .

I only have the one 18650, so up to this point I don’t have a need for a charger. I know what you are saying though. I just was wondering if it would be a problem to switch the cell out in future. When I do get a charger, it will be one of the ones that can do eneloops. What is a good 4 bay charger? I looked into the Xtar before but it has mixed reviews.
I have never seen that single charger. The problem I have with most chargers is that they have hit or miss reviews. I see that some reviews on Amazon show people getting DOA TC12s. I love mine.