. . . Also I know about imslp, I use to print classical music from there, but I have not been able to find scores from modern film composers on that site..
You won't find modern composers on the IMSLP site because composers must have died anywhere between 75 and 90 years ago for their music scores to be in public domain.
Chances are that scores for these movies may well not be available for purchase, due mainly to copyright reasons and or "performance rights" established by the composers and/or the composers publisher.
Have you tried direct contact to Zimmer and Howard?
Here's some info on them from the IMDB site:
There might be contact information for them there, or at least a link to their publishers.