Acceptance of Supplications even from sinners

In Surah Al-Zumar,verses 48 and 49, Allah mentions that:

"And the evil of what they have earned will appear to them; and that which they used to mock at will encompass them.
"But when harm touches a person he calls upon Us, then when We bestow a favor upon him from Ourselves,........"

In the above two verses, we see that Allah is oft-returning, and He returns with kindness even to sinners who calls upon Allah at their time of difficulty.