One way to check if your relative is pranking you, and since the sent amount is credited to your Ziraxia account, why not withdraw it to your non-custodial wallet, set up an Electrum wallet, and see for yourself if the amount can be withdrawn? I think only you can tell whether it is a prank or not since you have the amount appearing in your Zirixia wallet.
I received it in my Ziraxia wallet, but the transaction history is empty.
I would not say you were scammed by your relative until you told us that you were unable to move or use the funds sent and received to your Zirixia wallet.
My relative told me not to move any of the funds until extraction process is finished. If I do attempt to move the funds it may interfere with the extraction process. I guess time will tell. Once the extraction is finished I will see if I'm able to move the funds or if he asks me for a deposit into his wallet in order to do so.
Is API extraction a common form of sending BTC?
No, it is not a common form of sending BTC. He's probably messing with you.
Have you done any research on that "Ziraxia wallet" to see if it is legit? I've never heard of it and would rather stick to proven and reputable wallets when it comes to money. Scams with fake wallets and fake exchanges are the most common form in this crypto world.
Then why are there open source wallets that use API extraction methods?
There aren't.
https://techbullion.com/top-10-best-cryptocurrency-wallets-of-november-2023/Top 10 Best Cryptocurrency Wallets of November 2023
It's listed at #6
"Ziraxia Wallet: Known for its reliability, efficiency, and robust security features, ZiraxiaWallet remains a trusted choice in the market. Its open-end API Server enables integration with third-party software for enhanced functionality."