As is stated in the article EPDs and $ Indexes, you should never compare EPDs of bulls in different breeds. Each breed association has its own EPD calculations, using only its own animals, and with its own base point (the animals with an EPD average of zero). The averages and range of the EPDs will be different for each breed. A weaning weight EPD of +10 lbs might be above average for one breed but below average for another breed.
However, researchers at the USDA's U.S. Meat Animal Research Center, Clay Center, Nebraska have developed adjustment factors which can be used to estimate across-breed EPDs. You would add the adjustment factor in the table to the animal's EPD from its breed association, to give you its across-breed EPDs. These across-breed EPDs can be directly compared to each other.
For example, suppose the EPD for weaning weight for a Charolais bull is +25.0 lbs, and for a Hereford bull is +55.0 lbs. Just looking at the numbers, you might think that the Hereford bull is superior for weaning weight, and would sire calves with much higher weaning weights. The across-breed adjustment factors are 34.6 lbs for Charolais and -7.8 lbs for Hereford. Therefore, the across-breed EPD for the Charolais bull is 25.0 + 34.6 = 59.8 lbs, and for the Hereford bull is 55.0 - 7.8 = 47.2 lbs. You can directly compare these two across-breed EPDs. The Charolais bull has a higher across-breed EPD, and if they are both mated to cows of another breed (such as Angus), you would expect the Charolais bull to sire calves which are 59.6 - 47.2 = 12.4 lbs heavier at weaning than the Hereford bull (on average).
The 2016 across-breed EPD table is available online (the example in the previous paragraph comes from this article).