"servicios de traduccion de alta complejidad y gran volumen"

Hi there,

I'm a university student doing translation for the first time ever and did not realise how fine tuned it actually was. Am doing some homework and am stuck on the last line:

"nos especializamos en servicios de traducción de alta complejidad y gran volumen realizados por equipos de expertos traductores."

Now, I'm not asking for you guys to translate the whole sentence for me. The only thing I don't know how to get to make sense is "de alta complejidad y gran volumen".

High complexity and great size/volume? It doesn't make sense to say "We specialise in translation services of high complexity and great/large volume done by teams of expert translators"

May I have a little help please?
Thanks