here is my complete zapata.conf: 

[channels] 
signalling=fxs_ks 
usecallerid=yes 
rxgain=1.0 
txgain=1.0 
language=en 
context=default 
usedistinctiveringdetection=yes 
dring1=134,0,0 
dring2=137,0,0 

dring1context=internal2 
dring2context=default 


channel => 1 

here is the debug output: 

Aug 18 10:36:20 NOTICE[1112767280]: chan_zap.c:5053 ss_thread: Got event 2 (Ring/Answered)... 
-- Detected ring pattern: 137,0,0 
-- Distinctive Ring matched context internal2 
-- Executing Wait("Zap/1-1", "1") in new stack 
-- Executing Answer("Zap/1-1", "") in new stack 
-- Executing VoiceMailMain("Zap/1-1", "") in new stack 
-- Playing 'vm-login' (language 'en') 

this should have passed on to the default context... 134,0,0 also hits the internal2 context.