I use getalby.com to send zaps. In Amethyst, if you long press on the zap icon, you should see a button that will take you to Alby's wallet connect service so you can link it to the app. Check that out and see if it works.
Discussion
This is good. But I couldn't find Alby's wallet for Android. What's the name of the app? Or have I to connect my getalby account to an another wallet (e.g. bluewallet)? And a lot of wallet apps with LN capavility takes some fee after transactions.
You have to go to the Alby website.
Here's a guide for how to connect it to Amethyst: https://guides.getalby.com/overall-guide/alby-lightning-account/connect-your-alby-lightning-account-to-other-apps/connect-to-mobile-apps/connect-to-amethyst
And here is how to access the wallet via Zeus Wallet: