Obviously certain chords are easier than others. Check fingerings, and use open strings wherever possible. Remember that a viola section will play chords divisi unless otherwise instructed.
Double stops
Two strings sounded together. If the double stop is difficult (the left hand span is awkward) a section will play this divisi (notes shared out between instruments). Will work at any dynamic.
Triple stops
Three strings sounded together. A section will normally play a triple stop divisi (i.e. notes shared out between instruments). On a solo instrument, triple stops only work at loud dynamics, otherwise they would be arpeggiated.
About triple stops:
Quadruple stops
Four strings sounded, normally as an arpeggiation or broken chord. Four-note chords are no problem to a section if played divisi, but if non divisi then great care must be taken with left hand positions.
About quadruple stops:
Arpeggiation
Arpeggiated triple or quadruple stop.