Precise numbers, in some cases, need to be negotiated
A wizard 7/cleric 1 that employs the 4th-level Sor/Wiz spell animate dead [necro] (Player's Handbook 198–9) can control 4 Hit Dice worth of undead creatures per caster level that he's animated via the spell. This reader's always taken this to mean—unusually—a creature's total combined caster level because of the animate dead spell's unique mandate that restricts the number of HD of undead controlled "[n]o matter how many times you [the caster] use this spell [animate dead]."
Thus this DM would rule a wizard 7/cleric 1 can control 32 HD of undead creatures he creates via the spell animate dead, but this player wouldn't leave a campaign over another DM's ruling that the number is instead only 28 HD.
The feat Stitched Flesh Familiar (Libris Mortis 30), among its benefits, says that the undead familiar "grants its master the ability to control 4 more Hit Dice of undead than he is normally capable of controlling (both through the rebuke undead ability and through spells such as animate dead)." The rod of undead mastery (Magic Item Compendium 175–6) (10,000 gp; 3 lbs.) doubles the normal number of undead the rod's holder can control through any means. As both feat and rod use the word normal to describe how they alter the creature's ability to control undead, either the DM leaves it up to the player to decide how these two effects interact or the DM picks how these two effects interact.
This DM would allow the former if only because the difference between 72, 64, 68, and 60 HD isn't really enough for him to care about: a 12 HD skeleton is CR 6 and a 12 HD zombie is CR 4… and that wizard 7/cleric 1 has five more of them anyway. Whatever.
By the way, a wizard 7/cleric 1 through rebuking can end up controlling 1 HD of undead creatures. The rod doubles this to HD 2. Yay. Thank you, sir, and enjoy your ghoul.
About the domain Deathbound
The domain Deathbound (Spell Compendium 272–3) provides the cleric with the following granted power: "Your limit for creating undead animated with spells increases to three times your caster level instead of the normal two times caster level." This is really specific. See, the spell animate dead says that "you can’t create more HD of undead than twice your caster level with a single casting of animate dead" (PH 199). That means that the biggest individual skeleton or zombie a normal wizard 7/cleric 1 can create using the spell animate dead is 14 HD, but if that same dude has the granted power of the domain Deathbound, then the biggest is 21 HD. However, the granted power doesn't change at all how many HD of undead the dude can control, affecting as it does only the biggest he can create.
This is, believe it or not, a good thing as it's usually better to have one very big minion than dozens of littler ones… if for no other reason than so the other players don't get too bored while you take your PC's and his thousand minions' turns.