Where do the catabolic products of fatty acid breakdown enter into the citric acid cycle?

acetyl-CoA.

Explanation:

Fatty acids are broken down into acetyl-CoA by the process of beta-oxidation inside the mitochondrial matrix part of the powerhouse of the cell. Whereas fatty acids are synthesized from acetyl-CoA in the mitochondria.

Then acetyl-CoA which is produced by beta-oxidation enters the citric acid cycle in the mitochondrion by combining with oxaloacetate to form citrate and then complete the combustion of the acetyl-CoA into carbon dioxide and water.