This is the 11813th most frequent Spanish word.
haciéndolas
"Doing them" or "making them."
In this sentence, 'haciéndolas' is used to indicate performing the action of making 'las tareas' (the assignments) comprehensible.
Estoy revisando las tareas y haciéndolas comprensibles.
I am reviewing the assignments and making them understandable.
In this context, 'haciéndolas' refers to performing actions to ensure 'las medidas' (the measures) are effective.
Estamos tomando medidas y haciéndolas efectivas.
We are taking measures and making them effective.
Here, 'haciéndolas' signifies the act of ensuring 'las facturas' (the invoices) reach the clients.