Yes. Existing rules do  permit the following combination of degrees and diplomas whcih can be pursued simultanenously. The only condition is that if you are pursuing a full-time degree programme, then some universities prescribe that you take their permission before pursuing any other programmes.

a) You can pursue a full-time degree and part-time diploma.

b) A full-time diploma and a part-time/ distance learning degree.

c) A certificate in any mode can be pursued with any degree programme.

d) You can do two degres togather provided the graduating year does not coincide. Though some full time programmes actually restrict pursual of an additional degree simultaneusly.