Mini Forest Puzzle #2

PGN4:

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[Variant "FFA"]
[RuleVariants "CaptureTheKing EnPassant PromoteTo=BCFGIS"]
[CurrentMove "0"]

Difficulty: 1850.

Themes: Zwischenzug, Pin

Black/yellow to play and get a material edge.

The themes are Zwischenzug and Pin

Ic3+

Threatening Ixa1

Kxc3 then Cxa1

This line fails.

Then Cxa1

If Kxa1 Ic3#