Should i quit?

So currently i have a job on a zero hour contract. I consistently get about 4-8 hours a week. I love the job but it's just not enough to only be working a few hours a week. I'm applied for another job which is 30 hours a week, and much more suitable to my income needs. I think i could manage both, 34-38 hours when i have no other responsibilities seems manageable but of course since i don't have a set schedule for either job it's very likely that they would overlap.

I told my job that i would be fully flexible and i honestly think that's the only reason they hired me over other candidates, so if i tell them that i now only have very limited availability i fear i will seem dishonest.

If i even get the 30 hour job do you think i should accept it? If so should i try to keep both or just quit the 1st job.

As i said 34-38 is very manageable since i wanted a full time job in the first place but it's just the overlap in work times which is worrying me.

Of course, i may not even get the job and i'm worrying for nothing but it's something i want to know for the future anyway... in case i apply for any other jobs

How much control do you have over the job you’ve got now? In the end, it’s a zero-hour contract so you don’t have to take any of the work they offer you, right? If worst comes to worst and they overlap you can just tell the people from the job you’re at now, ’’no sorry I can’t take that shift, I have other commitments.’’ And even if you only get to work that job some of the time, or they reduce the hours they give you, you’re still doing better than if you just quit.

Take the second job if you get the offer. Explain to the first job that unfortunately they aren't offering enough hours for it to be affordable. If they offer you enough hours, they want to keep you, if they don't offer you enough fixed hours ie move you on to a different contract, then you owe them nothing.