I use the TMZ/Flagyl route if I am not really sure what I am dealing with (giardia or coccidia), that way I know I cover both. The TMZ gets coccidia, while the flagyl gets giardia.

However, if I had a confirmed case of Giardia, Flagyl and Panacur (fenbendazole) are what I would use, as they both work on Giardia specifically. It won't hurt to add TMZ, in case you have coccidia too, but the TMZ will do nothing for giardia (and, if you've already been using Albon unsuccessfully, that might be superfluous).

Was there any mention of coccidia also, or just giardia?