cross match in a worksheet depending on info in multiple dropdowns

Try this formula in C12.

=INDEX(INDIRECT("'"&C4&"'!C3:IQ78"),MATCH(C8,INDIRECT("'"&C4&"'!B3:B78"),0),MATCH(INDEX(Data!$B$1:$B$68,MATCH(C6,Data!$A$1:$A$68,0)),INDIRECT("'"&C4&"'!C2:IQ2"),0))

To test this I chose zaaizaden for the sheet name, Agave for the row lookup value and COMPOSITAE for the lookup value in Data which returns GB. Those point to cell O3 in zaaizaden sheet. I typed something into that cell and cell C12 in the Input sheet returned that value.

The file is attached.

Okay this is a step in the right direction. But the result zzzz should be given on "C4 zaaizaden C6 AGAVACEAE en C8 Agave". But C6 doesn't have to be included in the formula as it is only created so the list in C8 doesn't get to long. I tried editing your formula to

=INDEX('"&C4&"'!C3:IQ78,MATCH(C8,INDIRECT("'"&C4&"'!B3:B78"),0),MATCH(C10,INDIRECT("'"&C4&"'!C2:IQ2"),0))

But I keep getting a REF#

But C6 doesn't have to be included in the formula as it is only created so the list in C8 doesn't get to long. I tried editing your formula to

The C6 is included in my formula in order to determine GR. I didn't notice the drop down in C10 and overlooked that in the instructions. Apologies. My bad.

Try this formula instead.

=INDEX(INDIRECT("'"&C4&"'!C3:IQ78"),MATCH(C8,INDIRECT("'"&C4&"'!B3:B78"),0),MATCH(C10,INDIRECT("'"&C4&"'!C2:IQ2"),0))

New file is attached.

Super! You're welcome and thanks for the rep.